Wow! I had the DVD version (and enjoyed that) but the Bluray is in a different league. Really impressive. Picture quality is amazing, it almost leaps off the screen, 3D-ish. But admittedly there are a few scenes where you think "that looks a bit poor." The opening battle scenes are transformed (maybe Bluray handles 'gloomy' better!) ; the arena scenes are also noticeable better.
The second version (which, oddly, the director is at pains to point out isn't a director's cut) adds about 15 mins to the original. Some lovely added landscape shots stick in my mind. Most of extra seemed to be about the politicing of the republicans behind the scenes, and it did change the character of the film: made it not just an action movie, a bit more political.
If you enjoyed Gladiator on DVD, you must get this - you'll enjoy it all over again! A fantastic 7.99's-worth.