I've had no experience with Jennifer or April (Liaisons), but their reviews on The Erotic Review are outstanding. (check theeroticreview.com)
I can personally vouch for Nikki of Liaisons (bbbj, dfk, daty). I'm definitely going back there!
And, a year ago I had the pleasure of Christina (christinas-web.com). She is so skilled I was in a lust-haze for the entire time!