Thanks for the comments, everyone. Some responses:
Pazuzu - pretty much everyone on the Solstice forums sees the coupe as a future collectable, but they're a bit biased.
Talewinds - didn't know I was (in)famous on the Z4 forums. I was psyched about getting the Boxster, but the Solstice has a bit of the "road less traveled" to it, since I've done the Porsche thing before.The Solstice, the M Coupe, maybe I've got a weakness for orphaned cars. Maybe in order for me to get the Boxster, Porsche has got to stop production.
M21sniper - I'm happy with the performance, but I've got it scheduled next week for the GMPP (GM Performance Parts) upgrade; they chip the car to 290hp/340lb-ft, up from a stock 260/260 for $650; that's too good a deal to pass up. I also want to swap on the wheels from the Sky "Ruby Redline" edition. With that, I'll be set...
Masraum - the trunk is incredibly tiny, it's insane. I was actually worred I wouldn't be able to fit my 4" thick briefcase in it, and it's a near thing. My Z4MC is an SUV in comparison. However, we've already checked and a pair of soft-sided duffles will fit with the top down, enough for a weekend getaway, which is all you can ask from a roadster.
Ruflblackbird - window button and console switch placement is odd, with the assumption being you have the short arms of a Tyrannosaurus Rex (and yet, the wheel doesn't telescope towards you). I wouldn't mind as much if the windows were one-touch; the driver's side is only one-touch down, the passenger side not at all.
It's fun, and rather nice looking - I get as much pointing as the Smart, but people aren't laughing (kinda miss that).