Get a wheel! I couldn't imagine playing this game with a pad!
I do, even won (and lost...) a few races today in the online open lobby today (only started racing online yesterday, a bit late to the party) with all aids off (including slip recovery ofcourse) except ABS at 1.
In fact I find GT5 much easier to play without aids and with my trusted DS3 than Prologue whereby I always had to use a smidge of traction control on the more powerful rear wheel drive cars.
Unrelated, I don't understand all this, "what's there still left to do, I collected everything, etc.", though.
Sure collecting cars (or trophies now) is one of the most fun aspects of a GT-game, it isn't the main goal however, maybe I can suggest using them if that isn't an alien concept, I mean why collect them in the first place?
If you're only after collecting try focussing on the museum cards (pointless but a nice touch I reckon).
If you buy a game like GT5, then it isn't that illogical to assume you're heavily into cars now is it?
Drive them, tune them, keep them stock (if that's your thing), drive cars that aren't the obvious choice and drive them again.
If that isn't what you like doing than maybe it isn't the game for you, at least not for long.
It seems a bit like some people play it like they would play an FPS and only collect dogtags and weapons without an interest in the most fun part, shooting and killing opponents.
I'm a bit stuck on single player too by the way but online just gave this game a whole new lease of life, I imagined that it would and since you can host your own races (both private and in the open lobby) and therefore set the rules (which ofcourse are often ignored, that's also online unfortunately) GT5 became basically a new game to me again.
There's still plenty wrong with this game though (didn't want to end on a positive
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).