Very stable for me. I can't remember the last time I had a crash. Though there are lots of things in Sonar that I don't use. I record audio with MIDI drums - Superior Drummer, and one keyboard track, usually NI Vintage Keys B3 organ and that's about it.

http://axiology.bandcamp.com

Extremely stable here. The worst thing that's happened, which is rare, is getting audio pops when opening pre-X3 projects; closing and re-opening the project solves it.  
 
Have you done a reset AND rescan? That solves a lot of problems. Take the following steps:

• Launch SONAR and then go to Edit > Preferences
• Navigate to File - VST Settings
• Underneath Scan Options, place a check mark next to "Rescan Failed Plug-ins" and "Rescan Existing Plug-ins"
• Click the [Reset...] button
• You will be presented with the message: "This will reset configuration settings for all your VST plug-ins to defaults. VST Plug-ins will be unavailable until a VST Scan is performed. Any custom configuration settings will be lost. Are you sure you want to do this?".
• Click [Yes]
• Click the [Scan] button
• At this point, the background VST scanner will scan through your list of plug-ins.
• When the background scanner is complete, you can reapply and custom settings to your plug-ins

IMPORTANT: After going through this process, you will want to remove the check marks next to "Rescan Failed Plug-ins" and "Rescan Existing Plug-ins", especially if you have "Automatic Background Scan" enabled. Leaving all of these options configured simultaneously could lead to a continuous scan loop.

Detwoen
I'm going to start logging what I'm doing when it happens and see if I can see any pattern developing. I haven't done anything different to my system since the problem started happening so it's something already in my machine.

Really try to see if you can find a pattern - it may not be obvious and easy to find, though ...
 
For me Sonar is rock solid when working audio only (i.e. recording sessions, VSTs frozen) ... but I was suffering from a similar "random like crash situation" for a long time (and it actually just recently surfaced again), but it's very specific to MY system (in short: Octa-Capture drivers + several instances of multi-out Kontakt + low ASIO buffers) ... there's no cure for that unless NI or Roland improve their code, but I'm aware of it and can live with it ...

Solid as a rock here.  I had one crash with the Braintree release but it has been very stable since then.....knock wood!
 

I'm having the same problems except Platinum crashes almost every time work with it!  I was using Sonar X2 Producer until I recently upgraded to Platinum Producer about a month ago.  I love some of the new features and plugins that came with Platinum but other than that it has been a big disappointment.  I ended up having to go back to X2 because poor stability when using Platinum was ruining my creative energy and almost caused one of my projects to miss a deadline.
 
I'm also having some compatibility issues with "Cuba" - one of my plugins from NI Komplete 10 Ultimate.  When I would export my project all of the percussion from Cuba would be out of sync.  However when I would open the same project in X2 and exported everything was as it should be.  This was very frustrating because in my project I was using plugins that came with Sonar Platinum but I couldn't use these plugins in X2 because they were only "registered to be used with the Platinum version". 
 
I'm running Windows 7 64 sp1 everything up to date with an M-Audio ProFire 2626 w/latest drivers, i7 3770k, 16g ram with an Intel mobo.  The only plugins I use are NI Komplete 10 Ultimate,  all of the Spectrasonics line, and some of the plugins that come with Sonar.  I don't use any 32bit plugins.  My computer is totally stable with all my other applications.  
 
I guess I'll just wait for the next update from Command Center and give it another try. 

Platinum has been very stable for me (as was X3e), I can't recall it crashing or anything really, there might have been once earlier on where it crashed back to desktop, but I'm not sure if it was actually Platinum, so I'll disregard that 

Has to be a plugin or a driver... Sonar is pretty good.. Have you gone through the standard plugin procedures?
More or less covered above...
Latest Sonar is stable.

+1 for checking you are not running any 32bit plugins Dave. I had some older projects that had a single 32 bit plugin running under bitbridge that was causing exactly what you describe.

Detwoen
Hi
I'm knocked out with the monthly updates - fantastic stuff - but since it's been this way, Sonar on my computer has been much more prone to crashes than ever before. About every 4 - 5 sessions, I'll change a setting, might be open Melodyne, or select record on a track, or change a midi channel - little things .. and Sonar crashes. There's nothing consistent happening like the same VST instrument causing it, the things triggering the crashes could be anything.
 
Has anybody else noticed this? I'm certainly open to the fact it is my machine rather than Sonar, just wondered if I'm the only one.
Cheers Dave

+1 for checking fir any 32bit plugins Dave. I had a few projects with a single 32bit plugin wrapped in bitbridge that caused exactly the problems you describe.

Dave,
 
I didn't see your specs of your system/interface listed. Please list them so the forum can help you.
 
I will say it took a bit of a curve for me personally to get Sonar rock solid years ago. I've learned to have a DAW only machine with quality components and a higher end audio interface.

I was experiencing a general lack stability with Platinum - so much so that I was considering getting a new PC thinking it was my hardware instead of SONAR. Also after logging multiple calls I wasn't getting very far with Cakewalk support, they were trying to blame third party plugins etc. I was also experiencing an issue where Sonar wasn't remembering saved patches in Steinberg Halion, which they fobbed off as a problem with Halion. 
 
A good mate put me onto Studio One version 3, him having just cross graded from Logic, which I tried, no crashes, it's much faster and generally a cleaner DAW/Workflow than what is now a 25+ codebase that is Sonar.
 
Sorry Cakewalk but you've now lost a customer.