I've driven both the standard Sky and Sky Redline and they're not that great. Power delivery is OK, the gearshift sucks, the clutch is horrible, there is a huge blind spot at both front pillars, and the handling isn't very impressive. I had to pretty much poke my head out of the window to see around the hairpins at the reservoir here when I test drove them. You can really feel the unsprung weight of the wheels/tires too. That being said, I still want to buy one and fix those things. Well, except the blind spot. I love the clamshell hood (like a Corvette) and the access to the engine bay. There are some really nice touches under the hood that impressed me at the time (standard Sky), I don't remember what most of them were though. Plenty of room for an intercooler in the front, lots of room to route piping, etc. I didn't get a chance to look under the hood at the Redline, so I can't judge that.

Ecotec, rear wheel drive, big potential but pretty bad in stock form. I'd love to drive a modified one, just to see if the bad points can be fixed.

The standard Sky is an absolute dog, it can't get out of it's own way. My GF's dead stock Impreza Sport Wagon (2.5i) can destroy that thing on a twisty road. The Redline is a little better (well, it's more powerful at least), although it's no shining star either. I don't know what their weight is, but they're not light (and they don't feel light either).

I haven't driven a Solstice yet; I think they're ugly and don't have any interest in them. I'll wait for a hardtop to come out.