I generally only see movies in theaters if they're presented in DLP, and Riddick wasn't. After tepid reviews from friends (and worse from the press) I went into the NetFlix viewing expecting some cool visuals and not much else. 2 hours later, this movie went right on my xmas list, it showed up in my stocking (thanks, D!) and I just watched it again this past weekend.
I think it's a great movie! I can't speak to the sound as I'm only 2.0, but the story is cool and it looks nothing less than incredible. I also can't compare to the original release, but it's only a few minutes of added footage according to the box, and I only noticed the splices Twohy warns about in 2 or 3 spots.
This is one of the most underrated movies of 2004. At the very least, rent it, and if you like it, buy it, because Vin and Twohy are relying on DVD sales and rental figures to determine if there will be a 3rd installment in the Riddick series. (Which, BTW, if you haven't seen Pitch Black, wha...?!?!? One of best SF movies in history.)