I can't stand T-Mac's tone, and I really don't think much of his playing. I find him incredibly overrated and an untidy player (although that clip has probably the best playing I've ever heard by him).
Sherinian never plays anything I like, and I don't really like his sounds. Sheehan's technically very good, but I never really dig much of his playing. Portnoy? Haven't been interested in his playing for a long time now, and recent projects he's done have left me massively cold.
As best I remember, this was supposed to be a live band, and they'd be going around playing songs from their individual careers (why, oh, why would I want to hear Planet X's material played by the weakest members of the band and an inferior drummer in place of their star attraction, Virgil?), but it looks like there'll be a DVD available. This makes it sound like they'll be playing other "standards".