I've got heated seats and I actually like my leather interior, so I probably won't ever change it. I've seen some cool bucket/racing seats out there for other cars, I am sure it wouldn't be hard to do for ours. I'd say go for it! Half the reason I got an S40 was because there are hardly any around here and I like having a car people have to look at more closely to figure out what it is.
Dang, defeats the purpose of getting a volvo a bit doesnt it? That might be a deal breaker, I value my life and there are some stupid drivers out there haha. And most of all i value my neck/back so i like that whip lash prevention