I can tell you three cloud based PM's to avoid, IMHO...Colloborate MD, HealthFusion, and Intivia/Insync.
I have not heard of healthbiller.com but I have used free systems. The free systems are usually cumbersome to get around, and limited in functionality.
Would like your thoughts on why you don't like Healthfusion if you don't mind.
Which reminds me of one thing I don't like about Kareo, but have learned to ignore over the years...when you hit Check claims to check a claim for edits/modifiers(or even if you don't in some instances), it will tell you you need to add certain modifiers onto codes. And those modifiers are not correct. For me, I can overlook it, because I know it is wrong info. But for a newer biller, with an unfamiliar specialty? Could be very confusing