I'm on AMD 3.4ghz quad core with 4GB ram and IGP radeon 4250 (512mb shared). I first tried Ubuntu 11.10 back in early 2012, but gave up because my webcam wouldn't work, system would lag, mobile broadband would only work when using third party scripts, and Unity was basically featureless at the time. I was forced to use the open drivers because Catalyst has horrible 2d AND 3d performance on this chip. The open drivers are adequate but there are bugs with the desktop environemnts. I tried afterwards 12.04 which has a very pretty colourful interface, but again horrible performance with the laggy dash and laggy effects. To get it to be usable I had to use tweaks to disable features like blur, without which the dash text is unreadable, and had to disable the laggy compiz effects.
I tried E17 but it has the worst application support out of all desktops. Chrome won't work without system borders, basically rendering cutomizability function useless. Other apps have similar problems. KDE has a horribly ugly look and feel but I tried using it, but it has choppy opengl performance due to redraw bug which has been reported. It's not that my hardware can't handle it because every desktop effect runs fast if I switch on the FPS counter. The problem is to make any desktop usable, I have to tweak and disable half the features because of various bugs. Gnome Shell had great smooth performance in 3.2, but later versions were laggy.
I know that I should have chosen properly supported hardware from the beginning but some of these bugs seem to crop up afterwards. I've read reports of some hardware working beautifully when the older versions were released, and then problems when new versions are released. The bugs are OK but why does it take so long to fix them? Is the video chip I'm on very uncommon? I had bug reports from many months but no word on them at all. KDE is still unusable with desktop effects, so to use any DE, I have to disable features because of bugs which aren't fixed for so long. Now that gnome 3.8.1 is out, it has acceptable performance again and I like using it now, thankfully, because I don't like windows.
What are your hardware horror stories?