You should play with the wheel. I am using G27 with custom rig based on simul8or's blueprint.I've heard of the dreaded 5-3, I've done 4-3, and yeah they've mostly been "easy" - Only the quattro rally car caused a few restarts while i tried to grasp how nimble it was.
I agree with "learn-able" - I've already learnt quite a lot, I'm playing without the driving line which is a challenge for me in itself haha
The next step is getting a wheel, which I've always wanted to do (pricey)
Its good learning. The driving line is crappy though and doesn't help (at least for me). To be honest, I switched off all aids possible. No ABS (not even 1), no TCS, no ASM and none of those "high tech" driving aids. Its more fun to drive without them, but of course the learning curve is steeper. Learning to brake without ABS makes the game more engaging and gives more control over the car's driving characteristics.
Have to say again.... the driving line is crap. Its good learning tool on one hand, but doesn't help to improve lap times. The ghost replays are really good though! Must say PD did this damn right in the game.