Wow, what a hatefest. Let's join in.
HHKB layout - not for me, I couldn't get used that arrow layout.
Topre - also not for me, I don't like the feeling and I don't like that I can't change the feeling through mods. I think all Topre boards are overpriced. From a production perspective, MX boards require more work since the switches and diodes need to be soldered. So the extra cost is not justified, IMHO.
Model M - okay, but just okay, F is better. 2KRO is a bit of a deal breaker - membranes, yuck. Personally still prefer MX ErgoClears, though.
75% boards - why bother, you have to get used to a really funky layout and it's impossible to find replacement keycap sets. Still have to move your hand to reach F keys and arrows, may as well stick with TKL.
On the other hand:
60% boards - love them, especially when they are fully programmable like the GON NerD60 or have a really well designed Fn layer like the original Pure. Poker II style programmability is acceptable if you don't mind about the Fn and Pn key placement. Not having to move your hands so much to access F keys, arrows, edits, etc can be a boon to productivity if the Fn layer suits you and you take a little time to get used to it.
SA profile - love it, currently my favourite with Cherry coming 2nd.
Gaming boards - I'm allergic to the "gamer" marketing speak and overhype, but I'd consider a "gamer" board if it had all the features I wanted at a decent price and was made by a company with a good track record for reliability and support.
Smooth keycaps - I don't mind them, but it's nicer if I've worn them down myself. Gives a board some character, I like to see well-used products.