Well I am happy to report good test results when running Sonar Platinum 2016.12 with WASAPI enabled with my on-board Realtek audio chip.
 
Since everything was running smooth, maybe it was just out of curiosity, boredom, or a desire to stir things up, I made the change.
 
Disabled my FireWire audio, my FireWire PCIe interface, rebooted and enabled the on-board audio in my BIOS.
 
Set up the Windows audio for the HD audio playback device.  Then started Sonar, and setup the WASAPI exclusive mode @ 44.1/16.
 
Ran the wave profiler ... and got 10ms effective latency at 440 samples!  This is quite usable with soft synths. 

I think the biggest advantage is that it gives new life to old hardware. I have a remote setup using an old dual core PC and it's great. No need to invest in another interface. 20 year old mixer and 10 year old computer. Great for straight up audio tracking. 

WASAPI drivers development came totally out of the blue . . .
. . . who knew Cakewalk were even working on such things ?
It was never on their website for future developments. They clearly saw an opportunity and developed it right away.
Mobile recording and editing just got WAY more powerful on my laptop.
Maybe Cakewalk know what we need more than we know what we need.

This is great and means I don't have to drag an interface round with me all the time. 
 
Still need to do some more testing but it's been positive so far 

I was curious to see if the other audio apps that cohabit my PC would take offense to the missing ASIO driver.
 
It seems that WASAPI is only officially exposed in select applications, but in my case I also found a few that let me choose the MME driver, then under output device I selected something like "Speakers - High Definition Audio Device".  That is the name assigned by Windows to my on-board Realtek HD audio output.
 
For many apps beyond Sonar on Windows 10, there is good evidence that Windows 10 will now provide lower latency.  It seems that if either WASAPI or the HD Audio Device can be selected it may work fine.  I did run into a couple of exceptions below*.
 
In many cases, I  have no idea what the actual latency is, but hitting a key on my controller produced a note-on in a VSTi without a detectable delay.  So that much is good.  Microsoft must have tweaked their drivers in a recent Windows 10 update.
 
Host apps with virtual instruments in projects at 44.1/16:
 
Reaper 5.26 - WASAPI, Mode: Shared loopback(CAUTION), Speakers (High Definition Audio Device). No detectable VSTi latency.  11ms at 512 samples.
Ableton Live 9 Trial - MME/DirectX, Speakers (High Definition Audio Wave). No detectable VSTi latency.
VSTHost 1.56- MME Speakers (High Definition Audio).  No detectable VSTi latency.
AIR Ignite 1.4.1 - WASAPI, No detectable latency. Not actually a VST host, but does contain proprietary virtual instruments.
 
*Band in a Box 2017 with internal DXi synth - MME, Speakers (High Definition Audio), 104ms latency. Obvious latency.  This app is mostly used for playback, but if desired, a good workaround here seems to be to use a virtual MIDI port over to the synth rack in Sonar or another host for low latency real-time soft synth playback. MIDI thru seems to work in this case.
*MuseScore 2.0.3 with internal Fluid synth - MME, Speakers (High Definition Audio). Obvious latency.  No MIDI out port.
 
Standalone soft synths:
 
SynthMaster - Automatically detected the correct output (HD Audio). Playable.
Kontakt 5 Player - Automatically detected WASAPI and Speakers (High Definition Audio), with latency set at 448 samples , latency 10.2ms.  Playable.
Reaktor 6 Player  - Same as Kontakt Player. Playable.
Analog Lab 2 Demo - Automatically detected Windows Audio, Speakers (High Definition Audio).  448 samples at 10.2ms latency.  Playable.
Plogue sforzando x64 - WASAPI, Speakers (High Definition Audio).  512 buffers.  Playable.
 
Rapture - Nope.  Needs ASIO**.
Rapture Session - Nope.  Needs ASIO**.
Dimension Pro x64 - Nope. Needs ASIO**.
Z3TA+2 x64 - Nope.  Needs ASIO**.
 
** Thanks to VSTHost, the stand alone soft synths that require ASIO can have their VSTi plugs run in here.

Very nice report!
 
Thanks

When you run other hosts you're not using Cakewalk's WASPAI drivers.

ampfixer
When you run other hosts you're not using Cakewalk's WASPAI drivers.

Noel Borthwick [Cakewalk]
 
WASAPI presents the app with "endpoints" which can be multichannel or stereo or mono ...
 
And FWIW WASAPI isn't a driver model. Its a layer that talks to the WDM driver itself. So there is no such ting as a WASAPI driver.

 
It's actually a Windows thing, not Cakewalk ... Sonar just enhanced support for it.
 
About WASAPI
https://msdn.microsoft.com/en-us/library/windows/desktop/dd371455(v=vs.85).aspx
 
The Windows Audio Session API (WASAPI) enables client applications to manage the flow of audio data between the application and an audio endpoint device.
 
Header files Audioclient.h and Audiopolicy.h define the WASAPI interfaces.
 
Every audio stream is a member of an audio session. Through the session abstraction, a WASAPI client can identify an audio stream as a member of a group of related audio streams. The system can manage all of the streams in the session as a single unit.
 
The audio engine is the user-mode audio component through which applications share access to an audio endpoint device. The audio engine transports audio data between an endpoint buffer and an endpoint device. To play an audio stream through a rendering endpoint device, an application periodically writes audio data to a rendering endpoint buffer. The audio engine mixes the streams from the various applications. To record an audio stream from a capture endpoint device, an application periodically reads audio data from a capture endpoint buffer.

noynekker
WASAPI drivers development came totally out of the blue . . .
. . . who knew Cakewalk were even working on such things ?
It was never on their website for future developments. 

 
Neither was support for BLE-MIDI (MIDI Bluetooth Low Energy), but it was working at NAMM. Noel had Jamstik connected to SONAR via BLE, which even the guys at Zivix didn't think was possible. So you never know...
 

noynekker
WASAPI drivers development came totally out of the blue . . .

It is certainly great news that Cakewalk has chosen to work on further integration of wasapi and Sonar (just as they did with wdm/ks years before), but wasapi itself certainly didn't come out of the blue. Wasapi has been present and under constant development in windows sInce 2007. Since the release of windows 10 and it's improvements to windows core audio, wasapi has worked particularly well with Sonar. I suspect most people just didn't notice or try it until Cakewalk introduced 'exclusive mode' as a monthly update feature.
 
There is a great article on the history of windows audio (in which Cakewalk gets an honourable mention) here:
 
http://www.shanekirk.com/...of-windows-audio-apis/