In the 2.5 yrs I've had my Box, I've had tons of compliments from the people I run into. The only negative comment I got was back in Sep. I decided to drive the Box to the Neb - Wake Forest game in NC. On the way out I stopped in Chicago for a Cubs game. Scored a great parking spot just outside Wrigley "Stadium" (as Jeff Gordon calls it) on Waveland Ave. Had some time to kill before the game, so I was just hanging out by the car. A group of late teens walk by (3 guys, 2 girls) and the pack leader says "You oughta drive a real Porsh". I didn't bother engaging him but I thought to myself "Yeah, like the one YOU drive". I bet if I offered to trade keys with him he would've been excited.
As far as the 350Z crowd is concerned, they've bought the top of the line car in Nissan's offerings so they probably feel pretty good about themselves while us poor Boxster owners are just "entry level". Not sure what the G35 people are thinking. My sister bought a 350Z last Jan and I'll have a chance to drive it in a couple of weeks. I'm sure it's a nice car. She drove mine last year and was impressed but wasn't too excited about some of the reliability issues.
In the grand scheme of things, I don't need someone else's approval for what I choose to drive. I wave at the 911 guys that I meet and don't care if they don't wave back. If someone doesn't like my car, that's their problem not mine. I still have permagrin.