Using KDE in Kubuntu 9.04 (just upgraded to 9.10 today so can't comment on anything newer than Jaunty) at work as a software developer. I have to say, I'm not really sure what all the bad press has been about. The only issues I've had are when I tried to upgrade to the first KDE4 development version and was well aware that it wasn't for general consumption. After that I've not had any real issues with KDE on a dual display system. On occasion I find some of the plasmoids a little rough around the edges, so to speak, but that's down to the individual plasmoid developers, not KDE. On second thoughts, I lie, there was one issue which led the task bar to freeze for a few seconds whenever I got an IM in kopete but that disappeared in Jaunty.
I wouldn't say there are any glaring bugs or issues for day to day work. Heck, I use it here at home now as well and wouldn't say I've got issues with it when playing either. I think most of the big criticism comes from people who are still trying to use it like KDE3, haven't used it or are just trying to do odd things with it.
I get my work done and KDE doesn't get in my way. There are some things I don't like about it (dolphin, I'm looking at you) but that's personal preference. I'd suggest ignoring the peanut gallery and trying it out yourself, it's really the only way you'll figure out if you like it. Just try not to knock it for not being KDE3.