So I actually did buy a PS3 for just this game ($225 used 160 slim bundle off eBay). So I'm definitely a Twisted Metal diehard if I basically dropped $300 just to play it. Started playing it over the weekend and it's just what I'd expect from this franchise.
Single player is short, but tough. I'm on the last stage now and I'm sure I'll beat it in a day or two. It made me die enough times where I turned it off last night and I'll try today. Not controller-breaking hard, just enough to annoy you and require a very nice run to beat it.
Combat is VERY fast paced and intense. The charge and release weapons add a new element to gameplay. Cars are pretty diverse, but the specials are a bit generic (multiple cars with "chain gun"). Doesn't detract much from the overall feel though, and is probably needed to create balance.
I'll get to try out multi soon enough, but I'm excited about it. I also agree the maps are pretty phenomenal and have great layouts.
I also am a fan of the "Mario Kart" style races. Instead of just deathmatch, some of the levels require racing and shooting all along the way. Definitely a first for Twisted Metal, but it feels just right.
If you are only playing single player though, definitely wait for a price drop. Probably 10-15 hours of single player content, then the rest would be multiplayer.