Rarely, at least until about 6 months ago. The push for portrait-mode was the early reason people flocked to CSSU, which is why I avoided it as well. But the past 6+ months has been more about stability and replacing flaky Nokia bits where possible. I updated about a month ago, and am very pleased with the results.

I can tell you, I had issues with PR1.2 and 1.3. In particular, wifi would drop out on occasion, the graphics chip would wander off and cause a kernel driver to spin on occasion, and the dsp driver would occasionally just not work, causing camera and video apps to not work right. Updating CSSU brought along upstream patches for all of those, and now they're rock solid.

Want to see something you'll never see with PR 1.2 or 1.3? Check out the picture below, which I snapped earlier today. Note the up time, 3 week of solid running, and it's still doing well. This is my primary phone, and I use it constantly throughout the day. Web surfing, audio playing, email checking, texting, calls, everything. And yes, I'm running CSSU, with K49, and moderate overclocking.

I get that some people don't want to update because they're happy with what they have. If that's the case, I say go with it. Better to have what you want then chance for more if you don't need it. I totally get that. But I do think, if you're having any issues at all, CSSU will likely fix a whole lot more than it breaks. To date, I haven't found anything that CSSU breaks, but I'm sure it breaks something somewhere, as that's the nature of change.