I've had the new Aqueon 50 setup and running for a few days on my 55g. The pros and cons:
Pro: I like the filter cartridge fitment. The cartridge slides precisely into a blue plastic bio-grid, then that assembly slides into the HOB. No real paths for water to bypass the cartridge like on some other HOBs.
The unit self-starts so well, I didn't even have the power plug fully seated into the power strip and the filter had entirely filled itself and was pumping like mad.
It moves a LOT of water. The most I've seen out of a single cartridge HOB. Enough that I wish I could cut it back some. (to quiet it)
Cons: It is incredibly LOUD. Both in motor hum/whirr and in water splashing sounds. The outlet does not dip down into the water like on many HOBs, so there is lots of water droplet splashing on my vers-tops and NOISE. I did quiet the motor/impeller by disassembling it and greasing the magnet and both shafts with non-toxic plumber's grease, but it still sounds like I've got a Briggs and Stratton powered water feature running in that room. I'm sure the whole Aqueon HOB line isn't as loud, maybe this model is more prone because of the pump size and flow rates. I dunno.