Vista is buggy? I've been using Vista from about six months and I can count on one hand the number of times I encountered any kind of crash or BSOD that wasn't caused by bad nVidia drivers. It's about as stable as they come.
Vista is slow? My PC was never top of the range at any time, but I've never encountered slowdown running anything that wasn't either released in the last year or Supreme Commander on 81x81 maps. Speedfetch is made of win.
Vista is insecure? Quite possibly, but it uses Windows Firewall and Defender just like XP does. The only difference is that it has UAC which Microsoft have openly stated is designed to annoy users. The purpose is to force third party applications to stop demanding administrator access just because they can. I know what I'm doing so I just turn it off, and then I turn off the notification telling me I've turned it off. The whole process was painless and took me all of five minutes.
The Windows Update process is much nicer and allows you to postpone restarts, understanding that sometimes I want to finish my work before restarting so that the latest security update for a feature I don't use can install itself.
Vista is ugly? Maybe if you used it on a computer that was built when the world was panicking about the Millennium Bug, that might be the case but modern computers render the Aero interface beautifully and it's a great step up from XP's colourful but bland scheme.
I never understood the charge that it was stolen from Mac. The two systems are so fundamentally different that it seems strange that either could steal from the other. To me, Aero just looks like the logical progression of attractive user interfaces which MS have been introducing since Windows 95.
Vista comes with loads of new features which hardly change the world but certainly make using a computer more civilised. A good example is the "Open file location" function available by right-clicking a shortcut, trimming down the previous "Find Target" button in XP which took two or three clicks to get to. I also like the Vista Performance Index and I think it's a great shame that no one has bothered to use it. The idea that Vista is somehow a downgrade is laughably (and probably wilfully) ignorant.
Most of the criticism is a knee-jerk reaction brought about by a vocal minority who are terrified of anything new. They blast it for being buggy and broken when not only is it neither, but the OS has every right to be, given that MS built it from the ground up, taking not code but simply design principles. If you consider just what they've done, Vista is perhaps the most amazing operating system ever designed since Windows itself. They've built a platform that will tie together any selection of hardware (within reason), much of which won't be released yet, and then permits you to run any number of programs which again weren't necessarily available at release. It's certainly a far cry from telling a command prompt to print "Hello World", isn't it?
Next time you judge an operating system, judge it fairly on its merits on a system designed to run it. If I started railing against XP because it kept crashing when I tried to install it on an old Pentium II, I'd be accused of bias. Why does Vista not get the same benefit of the doubt?