PS forgot to say: I assume from the thread title you really do mean "M-Audio Hammer 88" and not "M-Audio Hammer 88 Pro" - the latter is about $200-250 more and a more recent release so I'm not sure there's so much about it in net articles and videos. But as I understand it it's basically about adding more controllers and stuff than anything specifically about an improved "action" ?
the Hammer 88 pro uses the same bad keyboard. I cannot believe those review that called this action "light". It is like glue. I pressed one key and I didn't like it instantly. I tried a bit more but it's not fun. Reviews write a lot of nonsense, even the good reviews are full of personal views that might not match your sensual preferences. the hammer 88 pro is overpriced. For 150 dollars more you can get much superior keyboards by Arturia and Komplete Kontrol (model name, not brand name) or Studiologic.
On top of that M-Audio's customer service is non-existent. Couldn't reach them by phone.
I also tested the Arturia Keylab 88 mark II which is the best MIDI controller as a controller and I loved the keyboard because it is direct. It has the Fatar TP/100LR keybed. It's been improved over the mark I.
Reviews had told me "there are better options" or it is "heavy". Yes, there is resistance. But you can speed up the key with strong finger action quickly - so it's a matter of strength.
The spongy keybeds like the hammer's you cannot do that. There is this resistance that is like friction.This shows you cannot go for reviews or what anyone says.
Form your own opinion and take your time. Buyer's remorse for keyboards is a bad thing and can spoilt the joy of learning and playing.
The third contender is an Arturia Keylab 88 mark I - but the asking price is too high and its older and I heard its keybed is not as good as the mark I. I'll likely try it out.
The Yamaha P-125 has a very good keybed and is in my opinion only second to the Keylab and the Kawai VPC controller.