I know this is a broad topic, but I'm a little out of the loop and am trying to step into the modern age (i haven't been on here in 2 years).

I currently have Sonar 8 Pro, running only one non-included VST plug-in called Izotope Ozone 3. My interface is an m-audio profire 610. I am running this on a windows 7 based PC build by Purrrfect Audio.

I'm thinking about upgrading to one of the Sonar X-series versions, but am not sure which one is best for me. The obvious choice might be Sonar X3 Pro (which i am looking at) but because this is relatively newer, i am afraid that it still may be kinda buggy. I also may have misplaced the Izotope plug-in CD and am afraid that when I upgrade i will lose the plug-in. This seems unlikely as I think it's simply a .dll file which shouldn't be altered during the transition, but I'm a little rusty and am not too sure of anything at the moment.

Q: In your opinion, is Sonar X3 Pro stable (as in lacking numerous bugs)?

Q: Would transitioning to Sonar X3 Pro, from Sonar 8 Pro somehow cause me to have to reinstall non-Cakewalk VST plug-ins (like Izotope Ozone)?

Q: This may be a stupid question, but... How different is Sonar X3 Pro from Sonar 8 Pro? In other words, will it be like learning to navigate an entirely new program? What, in your opinion, are the most significant beneficial developments made between Sonar 8 and Sonar X3?

Thank you and sorry for the extremely broad questions. If I am posting within the wrong sub-forum please let me know.

it will be like moving from a 1960's stick shift 1.2L car with 2 doors to a 4.0L BMW with a/c, electric everything, surround sound, sat nav..
Definitely get the producer version.. in this case you will get more than enough VST plugins in the bundle to keep you happy for ages.

try the demo

X3 has been a very stable release. The only issues that crop up repeatedly are turning off the 64-bit engine with X3c until X3d comes out, and the need to re-scan plug-ins after installation even if you don't think you need to. Sonar scans in the background and if you have a lot of plug-ins, this can take a looooong time. You might open a project and start work on it before the scan is complete and wonder what happened to your plug-ins. There's also a repeatable bug with the loop construction window where playback doesn't always start from the beginning, but there's an easy workaround I documented in another thread. There are some other issues, but most are relatively esoteric so most users don't encounter them. The core functionality is solid.
 
The biggest difference is in workflow. For me the X series is light years ahead and it's never been easier for me to sail through projects. That's the good news. The bad news is it's quite different from Sonar 8, so it's almost like switching to a different DAW. Functions you expect to find in one place may be in a different place, and so on. As a result, even though it's still Sonar you will experience a learning curve. However, IMHO the amount of time you'll save overall working in X3 compared to working in 8 will more than compensate for the time you spend getting famiiar with it.
 

I didn't even think about the possible road-block that I might encounter regarding the comparability of my Izotope Ozone3 VST plug-in. Is it possible that my older plug-in may not work within Sonar X3 Pro? This may be more of a question for an Izotope expert though.

I don't see any reason why Ozone 3 wouldn't work. After all, it's installed, and installing Sonar won't uninstall it. Also, I'm pretty sure iZotope keeps your registration info in the cloud. As long as you have your authorization code or serial number or whatever, you should be able to download it again if anything happens. But, I'm using a bunch of circa-Ozone 3 plug-ins with Sonar and it hasn't complained.

One more thing...using Plug-In Manager, make sure the folder containing Ozone 3 will be scanned or Sonar won't know it's there.
 

Q: In you opinion, is Sonar X3 Pro stable (as in lacking numerous bugs)?

 
For me, X3 has been the most stable version since 8.5.3 There are one or 2 minor bugs, but noshowstoppers, and for those that do exist, there are workarounds

Q: Would transitioning to Sonar X3 Pro, from Sonar 8 Pro somehow cause me to have to reinstall non-Cakewalk VST plug-ins (like Izotope Ozone)?

Nope - Anderton has addressed this fully in his post

Q: This may be a stupid question, but... How different is Sonar X3 Pro from Sonar 8 Pro? In other words, will it be like learning to navigate an entirely new program? What, in your opinion, are the most significant beneficial developments made between Sonar 8 and Sonar X3?

 
Phew! Where to start. The problem is remembering which features were included in 8.5.3
 

• Automation Lanes
• Take Lanes (supersedes Layers)
• Intelligent Colour Options (you can get tracks to follow Busses)
• Melodyne integration
• Pro Channel on every Track/Bus
• Completely redesigned GUI, which I think looks superb
• Brand new menu structure
• Control Bar replaces individual icons
• PRV has been given a huge overall from 8.5.3
• Many more plugins, instruments & Effects
• Tracks within folders are indented
• The core engine has been overhauled a couple of times

 
I'm sure there's loads more, but this should give you an idea about what's changed

Jonesey has listed many of the major changes, so I'll add just one more fairly significant change from v8 - the Smart Tool.  It means using the same tool in just about every view for most operations.  
 
Oh, and for ffb's benefit, there are Screen Sets. 
 

With X2 they removed the record button ;)