A little bummed that I encounter this constant bug with the PC version. The end of one piece of dialog gets cut off every time there is another chunk of dialog following it. The game seems to run very well other than that. But considering the overall feel of the game heavily depends on the dialog/voice acting it simply takes me out of the game - and it happens constantly (whether it's GlaDOS or the other little robot talking). There were some "solutions" I found on the official forums, but none seem to be working. When I verify the integrity of game data it keeps coming up with 1 file that needs to be reacquired, but steam doesn't seem to be reacquiring anything at all!
I realize this may not be the right forum to ask for tech support, but I simply felt like stating my frustrations here
Thankfully, the PS3 version is very well done, so I'll play that for the time being. Fingers crossed Valve fixes this.