What exactly are these bugs people keep talking about. I haven't experienced any.
I think there are a lot of features missing compared to previous UTs and I dislike many aspects of the art direction and audio compared to previous UTs but I can't think of any bugs I've encountered.
There's still crash bugs with the game on certain hardware, notably with X-FI sound cards that has onboard RAM when Hardware sound is enabled, but there's other crashes too, for me, i have to remove 2 Gb of RAM from my Motherboard to play UT3, or it will crash (i have no clue why, and nobody has been able to give me a good reason why this would be happening, or why removing RAM from my system solves it, all my other games and apps have no problems).
Then there's the infamous "Demo-Guy" bug, where all playermodels will turn into the same model if UT3 doesen't feel its got enough RAM, Epic says this is a feature to preserve framerates, players definately do not like it though, and would like it removed.
There's the "flying manta" bug also, where a certain combination of moves will make the Manta rocket into the air.
There's the "Duplicate login error" bug.
Eh.. and so on, there are still bugs, less than stellar hardware support, and instabillities on some systems aswell, all things that ought to be fixed.