There's always 'some' situations where a spare would be better, but to not consider years of driving bliss in an M3 because you worry about 'what if this happens' sounds silly.

You answered your own questions above Chonko! If you have a slow puncture and the dealer says no replacement available today, you put in the sealant and pump up the tire! Now you can drive for thousands of miles, waiting for the new tire.

Blow a tire? A run-flat? You would probably have more damage than just a tire! I haven't heard of a 'blown' tire since the Ford Explorer roll over days. That was due to overloaded vehicles with low tire pressure on defective tires. Run-flats don't blow-out. Correct me if I'm wrong. If it did, the answer is to tow the vehicle, get a loaner car from the dealer.

My Viper is a HUGE pain. It has run flats, and no spare. That's not the problem. There is no place to put the wheel/tire if you did have a spare! It will not fit in the trunk or passengers seat. Availability of a replacement? 345/30 19 Michelin ZP? Not at my Wal-Mart!

I will agree, a 'blown' tire far from home with no replacement available would be a major pain. Still not enough reason not to buy an M3!!!