Over the past year, I've been dabbling in some cam girl sites myself.
Like you, I used to use f4f. Pricy, but they had a lot of really great girls and the vid and connection quailty was usually quite good. Unfortunately, their customer service is seriously lacking and they've been driving some of their best girls away in droves of late. (Some seem to have left the biz, while others are working other sites.)
MFC has a great social atmosphere for members and opportunity to see a lot for free or with small tips. Low-cost group shows can also help those on a budget. The interface is really nice, on the most part, except for the fact that it really only works well with Chrome-based browsers. (I recommend Iron, which is an open source version without a lot of Google's overhead and nosiness.)
I also sometimes use
LiveJasmin. Much cheaper privates than the other two sites, but the interface isn't as good and there aren't near as many opportunities to get to know the girls or stay in touch with them outside of privates. Still, the admins do a great job with customer service support and they have been making a lot of improvements to the site in recent months. As far as the girls go...you have a better hit-to-miss ratio at the more expensive sites, but there are a few real gems if you look around. (And, granted, there are some girls camming at multiple sites, and their privates are usually cheaper at LJ.)
Cammodels.com/Streamate seems to be picking up some of the f4f-jumpers, but I haven't yet been able to figure out (without registering there anyway) how much shows cost. It's like they want to keep that secret until you get your first cc bill.