I've been using LR since 1.1, and have in general been extremely happy with it, I've rarely directly experienced annoyances or bugs with it.
Until 2.0--it's got me wondering whether I've got an installation problem or something. I've been using 2.0 for a couple weeks now on a mid-range year-old laptop, and while I'm very fond of many of the new features, I experience random hangs of the program for periods of up to 20 seconds, hangs the program never comes back from, random UI bugs creeping in (e.g., image info just stopped displaying (e.g., the "I" command), when I restarted LR it came back), weird screen artifacts during screen updating.
I have optimized the catalog as someone suggested, and that may have helped performance a bit but not a lot, I have also gone to find the "save XMP" entry another post described--but it was already off when I got there.
Suggestions as to what's going on here are very welcome.