FWIW, my personal rankings go
I like Saltalamacchia a lot, but there are just a few too many questions here.....1. Brian McCann is entrenched, so he will either have to move to 1B (losing a lot of value) or get traded, and then you never know what his new team will be like, etc. etc. He also had a pretty bad 2006 so it's harder to say anything for sure about how good he'll be. I know he was injured for part of the year, but that in and of itself is not particularly reassuring.
Iannetta is a peg down from Salty as far as potential, but a peg up as far as his probability of reaching that potential. It also doesn't hurt that he should be playing for the Rockies all season, getting at bats in Coors and with a good young lineup. If he can hit 15-20 HR and bat around .285 the next few years, he'll definitely be a worthy catcher in fantasy.
That being said if there was ONE less concern with Salty, he'd still be my guy.