Stable here, but I attribute that in equal parts to SONAR and to the computer I use.

Still on Hopkinton (W7 64 Pro, Focusrite Saffire 6 USB, i7 2.7 Ghz, 16 gb ). Not long ago I had a week where stability suddenly plunged to a crisis point, but since renaming aud.ini to something else, some 30 project hours ago, it's been like night and day, very stable for me. Projects include *many* comp takes, 4-5 Kontakt instances, a fair bit of traffic among aux busses, some eccentric automation envelopes and middling-needy FX.  

Got my first hang/lock-up of the day here, on a project that I've been working with for years. Audio engine's still running and I can hear my guitar through Guitar Rig, but Sonar's gone to the white-out screen and 'not responding'. Nothing to do with my machine, this is a software problem.

On closer inspection, this appears to be the return of an old bug where Sonar would occasionally freeze while saving. This has frozen during an auto-save and produced a truncated save file.
 
Further update: Sonar no longer likes (at least) one of the plugins (Ambience from http://magnus.smartelectronix.com/). It hangs if I try to open it and it hangs even if I try to delete it. I'll remove it in Safe Mode and see how things go - but this plugin worked fine for me with Sonar for years and it hasn't changed (while Sonar has).
 
Spoke too soon - bypassed that one via Safe Mode and now it does the same for another plugin. What they have in common is that they're both 32 bit. But I have 2 other 32 bit plugins loaded in that project that appear to work fine.

Kylotan
What they have in common is that they're both 32 bit. But I have 2 other 32 bit plugins loaded in that project that appear to work fine.

I wouldn't blame Sonar for not being able to handle outdated bridged plugins. It's like having worn out tires on a new car.

I would like 32gb inside

dappa1
I would like 32gb inside

Have as much memory as you want but 32 bit only addresses 4gb max.

hmmmmm......Mine hangs daily, or more frequently. Probably is my piano playing that does it...

I've been getting increasingly frustrated with Sonar Platinum. I've been using Cakewalk since the days of Sonar 3 Producer, and for many years never had any significant issues. I began having some issues with Sonar X3, but was hoping that was just a blip and Sonar Platinum would be a return to rock-solid normalcy.
 
But it really hasn't. It's stable enough for me to use, but only just. I contend with lock-ups and system crashes on a regular basis -- about 1 per day -- and have a few nagging problems for which I've developed work-arounds (eg, Sonar occasionally goes silent when loading synths, and when bouncing tracks -- it just stops talking to the audio interface -- and the only way to get sound again is to either close and re-open the program, or if I'm feeling lucky, I can try freezing and unfreezing a synth, which sometimes works). I've done all the usual chores -- re-profiled this, updated that, reinstalled the other thing; I've talked to Cakewalk Support, and got nowhere (their final word on the topic could be summed up thus: "well, you're using outdated hardware that is no longer supported, so you're kind of pooched -- but have a nice day and we look forward to your next subscription payment..."). The Cakewalk forums have been useful, and I've gotten a lot of help from my fellow users, for which I'm very grateful. But it really hasn't made much of a difference, and I'm beginning to get a bit weary of it all.
 
I genuinely love this software. Sonar's intuitive, elegant interface is second to none, IMHO, and it has peerless workflow. It sounds awesome, comes with a ton of genuine goodies, and I'm very comfortable in its environment. But I'm getting to the point where I no longer trust Sonar to come through when I need it, and I am seriously considering moving on. I have a decently spec'd iMac sitting in the next room, and have been eyeing the UAD Apollo interfaces and Logic Pro X. I hear nothing but good things about all of them, and that comes to mind every time Sonar hangs on me (in other words, every day)...
 
 

Had my first "scary" crash last night.
Working on project "A", 8 audio tracks, 1 MIDI/Audio combination. No track plugs, only ProChannel compression on most tracks, 1 reverb send bus. Recorded the synth track to a PatchPoint audio track "live", deleted the MIDI/Audio combo, saved and exited. Nothing major here.
Opened project "B", 8 MIDI/Audio combos, 1 audio track. Re-recorded one of the synth tracks to a PatchPoint audio track. Deleted the newly recorded audio track (from the patchpoint), exited without saving.
Tried to open project "A" again, no go, SonarPlat crashed. Closed and reopened Sonar, try to open project "A", crash.
Reboot computer, open project "A", crash again. Obviously, something in the project was corrupt.
Closed Plat, opened X3, open project "A". Warning that it was saved in a newer version and would lose settings from the newer version that were not supported. Project "A" opened in X3. Saved the project in X3, re-opened in Plat, this time opened fine.
Something in one of the new features, possibly PatchPoints, needs a little more time in the oven.
It was late, so I didn't spend a lot time trying to isolate what "I" did to cause the corruption. If I get some time today I'll try to reproduce.
For a few minutes it was a bit scary to have lost the bounced project, but X3 came to the rescue. I can't remember the last time X3 crashed on me, so I'm a little uneasy about Plat's stability as of last night.