It's the hardware and it's design that sells to the mainstream consumer, ICS on the phone is a plus but very few consumers care about that. My point is that Prime is too hot for Verizon to pass on.
From Verizon's stand point, with the tiered plans in place, they can counter the "openness" of the phone by "forcing" you onto tethering plans if you do so (all carriers can detect this, T-Mobile is the only one not charging) which is pretty much the only "damage" rooted phones can do so they maintain their grip, business as usual.
Yes, they do like their bloatware but has that stopped Verizon from getting the iphone, which they couldn't lay a finger/app on?
Again, it's all a matter of hot handsets, if you got one, like Apple does, then you can twist the carrier's arm a little.
As for exclusivity, it's either going to be temporary or other versions will be launched simultaneously.
The recent disaster in Japan has slowed down the tech industry, I think the Prime and the iphone 5 will set the bar higher again. Until the 1st quad core phone shows up.