I've done some searching and found results from a couple regional events regarding the 350Z and auto-x events. Is the car considered competitive overall, and enjoying anything near the level of enormous success of cars such as the M3 (E30/E36 mostly), S2000, Corvette C4/C5 respectively (to their introduction and in some cases, continuned dominance)?

I haven't attended an auto-x event since I drove my A4, but am looking forward to trying one this weekend in the 350Z. Also, I've done a couple of events at "Streets of Willow Springs" with the Alfa club and the really nice folks of Porsche Owners Club (not to be mistaken for Porsche Club of America - who is far more 'white gloved' IMO). I'm going to see about an upcoming "Streets of Willow Springs" event as I find that track a lot more fun that local auto-x but not an intimidatingly fast track (the new expansion does make it quite a bit longer though). So if anyone would like to attend I'll set it up. Right now, I think I'll go with the Porsche Owners Club in the 3rd week of May:

Porsche Owners Club

(under events)

It has been some time since I joined them, but my last two events were great fun and they run the track very professionally.