I've auto-x'd by 350z a couple times; never got to be all that great in the three events I attended nor wanted to be due to the burning up of tires (even though I used my old stock rims - 17" as opposed to my daily 19"), etc. over the course of several events... Plus I daily drive my Z (2003 with 102k miles now!!) so unnecessary abuse (other than my daily "spirited" driving) really isn't in the cards for me until I pick up another vehicle.
I really enjoy(ed) it, but there are just other hobbies I'd prefer to spend my $$ on including brewing (i have to say that here), road-biking, etc. I still use the Z as a hobby, but mostly just attend meets and "cruise" type events. I'll have to post some pics of my first auto-x event when I get home (photobucket blocked at work, boo!)...