For me, it depends on your definition of Mastering, and what medium being mastered to. Obviously, if you ask an engineer such as Bernie Grundman, Dave from Lucky Lacquers, or even any Vinyl cutter over at United what their definition is, they may not feel Sonar's Mastering capabilities are the true definition of Mastering, but when you take your project to someone who can master it, it'll likely go into a DAW and be pushed out as a CD-R. I think Sonar can do some Mastering functions, but it still really lacks the metering, and work-flow. People have been using PT for years to Master projects, but what overkill use of a resource.
 
I still use Wavelab, since the latest version comes with a DDP encoder, a brand-able export reporting tool, the ability to build a montage and assign markers that translate fully into a CD master, and great metering. Plus, the workflow is second to none, IMO. With that said, simply exporting a great-sounding (or even smash-limited) single is nothing Sonar can't handle, for sure.

StudioOne also features DDP.

With cd's being burned less for delivery DDP & PDQ would be 1st priority if Sonar wants to be a viable mastering application going forward.

(HOFA also has a plugin that works in Sonar plus an excellent stand-alone program as well)

Dream Logic Audio
I totally support this.  I do most of my mastering in Sonar already with the help of some 3rd-party plugins, but having this functionality built in would add even more value to the program for new users.
 
 If Cakewalk is smart, they will put Craig in charge of project development for Mastering Enhancements. (You're welcome Craig!) 
 
In addition to what has already been suggested, I would LOVE to see K-System Metering as an option for the built-in Sonar meters.
 
Kenn

Kenn, I agree.  I already do most of my mastering in Sonar, but with existing tools.  I would like to NOT have a separate program to support mastering, and would love to be able to do it ALL directly within Sonar.  This, along with enhancements to Editing are what interest me; not additional midi instruments.  
 
I would also like to see more enhancements to metering.  

Can someone explain what's lacking in the metering in Sonar?
 
I always set my meters to show both RMS and peak.  Plus, I used another free plug-in called TT Dynamic Range Meter, which measures dynamic range for an entire song, album, whatever.  Nothing past these things matter to me.

POst # 45 by theheliosequence
 
This was the best post from my perspective. If you have never used proper mastering software like say Wave Lab or Sound Forge you just don't get it. 
The best line was this: 
A proper wave editor. When I double click on an audio clip I don't want to go to a loop construction view... I want to go to Sonar's new audio editor. That has tools for fixing digital errors, clicks, tape hiss, vinyl pops and scratches and maybe even a de-clipper.
 
This has been my one and only feature request and so far I've received zero feedback from the forum when ever the subject is brought up. Just like you'll see his post was ignored even though all his points were excellent.  It's like no one understands the power of direct wave editing and how mastering is really done by the pro's. We are forced to "tool copy" into a wave editor to fix little burps. Sure Sonar can do a few of these things but only after a ridiculous amount of mouse clicks. In a wave editor its a quick operation that can be repeated without re opening a process gui. 
 
I already own Wave Lab so I don't care if Sonar ever includes Mastering as I would not want to re learn in a new environment. I'd continue using Wave Lab because I know it better than any software I own. But It would be sure handy to have a wave editor in Sonar. 
 

MondoArt
Can someone explain what's lacking in the metering in Sonar?
 
I always set my meters to show both RMS and peak.  Plus, I used another free plug-in called TT Dynamic Range Meter, which measures dynamic range for an entire song, album, whatever.  Nothing past these things matter to me.

Discussion's going on about metering in the Techniques Forum.
 
http://forum.cakewalk.com/KSystem-Normalize-before-entering-Sonar-m3210437.aspx
 
http://forum.cakewalk.com/KSystem-Confusion-m3195674.aspx
 
 

MondoArt
Can someone explain what's lacking in the metering in Sonar?
 
I always set my meters to show both RMS and peak.  Plus, I used another free plug-in called TT Dynamic Range Meter, which measures dynamic range for an entire song, album, whatever.  Nothing past these things matter to me.

Be aware the free TT-Dynamic Range meter was stopped being offered by brainworx because of issues with Pleasurize Music.
It also known to be inaccurate & has since been replaced by the meter available at Plugin Alliance.
 
EBU compliant metering is the current way forward. Others daws have had them for several years & should already be included in Sonar Plat.

The HOFA 4U Meter is an excellent freebie.
http://hofa-plugins.de/en/plugins/4u/

 

theheliosequence
But what could Cakewalk include that would be really cool and/or allow someone to stay in Sonar and deliver a master to a manufacturing plant?
 
An ISP (intersample peak) monitor.

 
Meanwhile, you can use the free SSL X-ISM plug-in, put it in an FX chain, and stick it in the master bus ProChannel 
 

A LUFS meter. 
DDP creation.

 
Solid ideas and probably relatively doable, assuming there was a CD assembly page that merited having DDP export. But..we also need to be realistic about how many people are making CDs these days vs. how many are streaming/posting on the web. 
 

Sample Rate Conversion

 
The workaround for now is to export the tracks, then bring them into a project with the new sample rate. The algorithm quality is certainly up to the task.
 

A proper wave editor... hat has tools for fixing digital errors, clicks, tape hiss, vinyl pops and scratches and maybe even a de-clipper. Powered by iZotope? Even better!

 
A lot of what you're talking about is restoration, and those kinds of tools are quite costly. The "basic" RX4 is $349, so licensing something with that functionality would raise SONAR's price considerably. As to the $1,199 version...that's twice as much as SONAR Platinum! It probably makes more sense for people to buy RX if they need it rather than make everyone pay more for SONAR, regardless of whether they plan to do mastering or not. 

brconflict
For me, it depends on your definition of Mastering, and what medium being mastered to. 

In my seminars on mastering, I differentiate between "Mastering" with a capital "M" (i.e., a mission-critical project that's crucial to a career) and with a small "m" (what gets posted on the web or put on demos, but needs to be much better than the raw stereo mix). 
 
Every now and then SONAR surprises me, like the time I got rid of a digital click by cutting the individual clipped samples and replacing them with individual samples copied from either side of the click. For me, with a properly recorded track mastering is 85% EQ, 10% dynamics, and 5% waveform editing (e.g., bringing an isolated snare hit up +3 dB, shaping a fadeout). AFAIC SONAR has EQ that's up to the task, with the LP-64 for precision and the ProChannel for more "character" shaping; the waveform editing is good unless you need to do surgery. I can even do my "micro-mastering" trick to get volume while retaining dynamics with SONAR...the "Find Peak" function (that's also found in Wavelab) is really handy.

Anderton
I don't know of any DAW that has this built-in (except for Reaper's plug-in, which I haven't tried so don't know how it stacks up against SF or RX), so SONAR's not unique. I assume that's because it's a fairly complicated offline process.

 
Not sure if Audition counts as a DAW or not (I use it as an editor rather than for recording or mixing) but it can handle multitrack audio and has decent noise reduction...