I use a g27 and have never had an issue with the 180 degree on screen steering action as I'm looking out of the window and can see my actual wheel in front of me. I think cockpit view adds to your immersion and is, for me at least, closer to driving a real car. Which is the reason I bought GT5 as opposed to NFS etc.
GT5 is a game that you get out what you put in. If you turn all the assists off and alter the settings to their most realistic, pick appropriately powered cars/tyres for the opponents you're against the game will have alot more of a pretence to realism. Or If you want to put racing softs on everything and drive a 900pp car in chase cam with all the assists etc. on it will play like an arcade game.
Different strokes for different folks, a lot of posters on here would do well to remember that.