Too risky for me
I had to renew 323 .US domains, so I considered using iDotz.net because they were offering a $4.95 ".US bailout package" (I have to admit the promotion was funny). So I would have saved about $650 by transferring there instead of sticking with my current registrar. But I decided against it.
First of all, they don't even seem to have a bulk transfer form, so you have to paste the domain and auth codes in one at a time. And my experience is that if a company makes even transferring IN hard, transferring out (when I need to) will be a nightmare. Plus it sounds petty, but it swayed my feelings that their own domain name (idotz.net) is so lame. And they don't seem to be ICANN accredited themselves. Instead they use Key-systems' RRPproxy system. But what spooked me the most was a story on DNF (part1 ,part 2 ) about a guy who registered some .info domains there under a "free" promotion. They apparently ended up charging him anyway due some fine print in their promotion, plus they refused to give him the auth codes when he wanted to transfer out and he only got his domains transferred after months of work and intervention by Afilias. This is an old story (2004), but they seem to have the same set up and management. I went as far as creating an account, obtaining the auth codes for the 323 domains, and moving some of them into my idotz cart (one at a time, argh!), but in the end decided to steer clear.