It has worked OK for me. Seeking is not very fast and usually causes noticeable audio corruption and stutter for a while, as the player tries to catch up. The biggest issue for me seems to be if the disc is not spinning fast enough then playback will be choppy, but I have a similar problem with TMT3 only not as bad. I don't know why or how, but it seems PowerDVD is somehow more efficient in reading data from the disc, as when spinning at the same speed a movie might play fine in PDVD but will stutter in TMT3 (and MPC-HC).
I haven't used it all that much, but so far I've only come across one disc that was completely unplayable, and that was the UK release of Serenity. It plays fine for about 10 seconds, then starts to stutter like crazy. If you go back to a section that it has already played (stuttered) through then it'll play fine, up until the point where you last went off. It's like it's processing the movie as it goes, and only until you've processed a section once does it play smoothly. Weird stuff (plays perfectly in PDVD and TMT3 of course).