I got GT5 for my birthday, and I am really enjoying it so far. It's just like the other GT games and I guess that's why I like it. However, I do have a few gripes about it so far.
First, the loading times are atrocious. Every time I change a menu it's a 20 second load time, and I did install to my hard drive, so I don't know what's going on. Maybe I need a faster hard drive. But every 2 seconds, it's LOADING or SAVING or INSTALLING, I mean wtf. I just want to race, I don't need super fancy menus with tons of graphics that take 20 seconds to load. You're wasting my time.
Second, the race requirements are bad at explaining who's eligible some times. For example, the Lightweight K Cup lists about 40 cars I can use, but it doesn't give the stipulations (e.g. cars under 800 kg or something). Other races do, though, so I don't know why they didn't do that with all of them. In the older games, the stipulations were listed very well I always thought.
Third, the graphics in some spots are awesome and in others are bad. I don't know why that is, but I have seen views around the car that look amazing, then later I see views around a different car that look very bad (e.g. before the race starts, some of the cars look like ****).
Fourth, why did they move towards driver levels and restrict races? I mean, if we have levels, what the hell is the point of the licenses? The older versions used licenses to prevent you from racing in other races too quickly, but now we have levels and licenses. Seems redundant and foolish imo.
The game mechanics are pretty good. But still it has an arcade-like feel. It feels like they took a lot of cues from Forza on this GT, but that may be because I put 50 hours in Forza 3 before this.
Either way, I still enjoy the game and will be playing it quite a bit.