I'm liking the new Guillotine and Lancelot. (and the Lancelot really needed some work). The Mongoose looks like an updated version of itself, which is also good.
I find the new crab's forearms a bit too chunky, but it fundamentally looks like a crab so I can't really complain.
After that...
I'm sad to say that if the Crockett wasn't labeled, there is no way I would have recognized it. It's not a bad looking machine, but I find it totally forgettable. I feel like the new thug leans that way a bit too, but retains enough essential "thugness" that I still like it. I can live with the new Crockett, but I suspect somebody will have to remind me what it is every time it appears on the table.
The Flashman on the other hand is a total miss for me. The old design needed help for sure , but after seeing the brilliant resculpt IWM put out in conjunction with Behrle Hubbuch and Justin Nelson, I am unconvinced that we needed a whole new Battlemech. The new design isn't bad, but it looks like it has replaced the slightly aero / art-deco design aesthetic of the Star League era with a much more angular WoB kind of look.
I think part of what makes me like the new Black Knight so much is that it updates the whole design while keeping some of that unnecessarily streamlined design from the original SL collection. In my own head, that look provides a subtle cue to designs originating from an imagined golden age.