I'm thinking about buying a Surface Pro 3 for Christmas and was wondering if anyone had any experience with SONAR X3 on such a system.  Any feedback would be helpful.

I have no experience with this one. I did run latency-mon on a PC at Best Buy that was much like it and it passed the test.
 
I've been sort of interested in something like this myself. Currently, when I want to use a Windows Laptop to record, I borrow my daughters. For performance purposes, a slate like this would be much cooler.
 
Let me know how it works.

My wife has a Surface Pro 2 and I've thought about installing sonar on it to see how it works. haven't been able to get it away from her long enough yet.  and she's had it for a year...
 

I have wondered this too. Surface 3 pro is much more powerful than 2. I often go to MS. I think I will ask if i can install x3 on one to test

Wasn't there something last year (give/take) about Android devices having unacceptable latency for audio recording? That you needed an iPAD to get what you would want?
Then with audio recording, direct monitoring should make it a moot point. I guess, and I am a MIDI dummy, that MIDI, especially with any FX is where the rubber meets the road.
I would really like to know the skinny on this because I have put off buying an iPAD but would really like a device in that category to use for playing around. I don't need it by any means but I want it... also to read magazines etc. I have a Kindle for books but it isn't so good for magazines and the Kindle Fire just does nothing for me. The Surface Pro or some other device with a screen near the size is appealing, if it will be useful for IK stuff and things like Audiobus. IDK... but I'd like TK!
 
J