My experience with ProgPower is that I usually know 1/3 of the bands really well at lineup announcement and after exploring the other bands that I wasn't familiar with; I usually find that I really enjoy half of those bands. This is actually one of the things that I really like about the festival - getting to know bands that expand my listening interests. Hell, there have been a few bands that at line-up I thought "Glenn, you've got to be kidding" and then I go on to really enjoy them. DSO is the poster child in this case. I still grin when I think about their performance!
Of the bands that I didn't know well this year, so far I am really getting into Voyager, Mob Rules, and Sanctuary. Voyager fits very well with my progressive preference - I really like Element V. Thrash is another favorite genre and I like Nevermore, so Sanctuary is resonating as well. The biggest surprise for me, so far, is Mob Rules. There is something about their name and artwork that said "mindless powermetal" to me, but Mob Rules really stands out with their emphasis on melody and sophisticated song writing. I find that I like their most recent releases the most, both of which have extended pieces. Their most recent CD has an 18 minute epic about the assassination of President Kennedy - nothing mindless here. To be honest, Therion for me is a bit like your first sip of Jack Daniels - but by festival time I will probably be hooked. Also, I am finding that Dream Evil is pretty easy to get into.
There will probably be a few bands that after giving them a try I will decide to go shopping, drinking, or socializing during their set, which is fine too. Actually, this year the overall lineup is so damn good that I am concerned that I won't have enough time to shop, drink, and socialize. Not a bad problem to have!