When people ask for a recommendation, I tell them if they have cards that fit old company's requirements (10k minimum, 5+ years old, Barclays, Capital One, Citibank, Discover, Elan, PNC, US Bank, USAA, Bank of America, Chase), enroll there, if not (if cards are younger/lower limit), enroll with new company.
Still haven't found any other companies worth working with, and occasional sales with cards that are newer are worth it, but yeah, the volume isn't as good (or saturation is higher), unfortunately.
Go between those places where your cards fit, basically.