I’d like to echo this question - I’ve never used IceWM extensively, but I’ve considered using this window manager on several occasions, and in general, I have a good opinion of it.

So, I'm curious if there are any rough edges in it.

I personally haven't found rough edges in it other than it will not really be a modern UX if you're looking for one. If you're comfortable with IceWM's UX then it's fine.