I don't care for Acclaim at all (just to show you that I'm not partial to them), but when I saw my friend playing this game I knew I had to rent it my self. This game is truly original, with many improvements (in my opinion, of course)over THPS3.
Firstly, there are two major differences between the Tony Hawk series (as of now) and Agressive Inline. The first one is the removal of the clock, which is indeed very refreshing to me, as I like to explore, as I'm sure many others do as well. The second change is that each level carries 20 - 35 challenges, and while there some of them are just clearing specific gaps, the game does feel much more expansive.
But perhaps the little things are just as important. Now, instead of finding stat points and getting to assign them to any catergory, each collectable stat point is already assigned to an attribute. And most aren't collectable at all, instead you earn XP (experience points) to increase your skill the more you play. There are tons of juice containers to collect as well, as well as orange ones that increase your juice meter's maximum. Other collectables in each level include a key in each level which opens up a sometimes massive part of another level, and a special move in each level.
As for the tricks, some may find them too easy. I'm saying this because I'm not all that great and find it possible to revert and manual my way to a 50 million point trick. That's not really the point, as this game revolves more around hard to find challenges than points, so you could compare this game with something from the adventure genre.
Grahpics-wise, the game is certainly passable. Most of the music is not of my taste, but Acclaim does let you remove tracks that you find particularly annoying.
All in all, i'm very impressed with this game, especially considering the company that produced it, and I encourage fans both in and out of the genre to rent this game. I have a very good chance of buying this game used in a while. Enjoy it, it's a great game.
One warning though, it takes 57 blocks on a GC memory card, and while there are many stats to be saved, this is far too much.