Ever since 3.0, from my perspective, the kernel went to hell in a handbasket...
Around 3.0 is where the kernel platform drivers broke my wireless in my 7 year old HP laptop which was working perfectly fine for 6 years until then.. I've had to blacklist the HP platform driver to fix it.
They tell me to test the latest kernels (3.5 head, 3.6 head, etc.), but these kernels lock the system hard on the same laptop, so they won't even boot. The only solution that works perfectly is kernel 3.2 in Debian Wheezy and on top of that, I have to blacklist the HP platform drivers. If I do that, the system is rock solid stable and the wireless works flawlessly. it's also works flawlessly on 2.6* and 2.4* kernels since forever..
Then I bought a new laptop.. Turns out Kernel 3.2 that works perfectly on my other laptop, in Debian Wheezy, randomly locks up hard when running iceweasel/firefox on this new laptop. In fact, it seems to be a common occurance for people with mobile Ivy Bridge processors and intel graphics. I'm so lucky that the 3.5 head and 3.6 head kernels actually boot in this new laptop (although they don't on my other), and not only that, but it fixes the lock ups.. Why haven't the fixes in 3.5/3.6 been backported to 3.2 stable? I have no f-ing clue. Apparently the kernel team is leaving it to the poor folks at Debian to find these crash fixes in the mess of the 3.5/3.6 kernels and backport them in the hopes of making a stable kernel themselves because the kernel team isn't providing a stable 3.X release (yet!).. IMO, it feels like the kernel is a horrible mess right now. I've got 2 laptops that require very specific kernel versions (that are different!!!) to function at all, which means to me that the whole 3.X series is terribly unstable.