I've been playing it, as well. (BTW, the parking brake is the R1 button.) The analog control is a bit weird to get used to but once used to it, is much better than using the digital control for steering. You can change these in options, I believe.
There is some tuning that is allowed if the car you have is 'favorited'. Also, I'm not concerned with the lack of parts or in depth tuning simply because I enjoy racing the cars as they are. Stock for stock. That's the whole point of a sim to me. Not to Nascar them out (or whatever other racing that's comparitive) making them all the same fuckin car with different names.
Completing challenges will unlock a couple things, not only give you money. You can also play your own music while you play once that is unlocked. There are more challenges than you think.
Endless stream of cars, shit loads of tracks, some I've really fuckin missed. I do miss the lack of a sim mode as in previous gt's.
Also, in options, you can install the UMD and drastically reduce load times. I suggest you plug it in for this as it will only take 15min to install that way. Norm installed his while riding in the car with me and it took 45min.
It's pretty easy to make money and you can earn cars at a rate of 10 to 1 compared to how it will be in GT5. You will also be able to transfer your garage to GT5 once it's released. I personally will not be doing that. I would like to start fresh.
I know I'm missing some things and shit, but that's the gist.
I feel they really hit the spot just enough to fill in the void until the middle of next year and the release of GT5. Bastards.