Thanks! The feel of the enemies and making them really distinct was indeed something I focused on :).
The comments I hear most often are similar to yours: the game is good, but it should have more enemies/stages/moves/upgrades - more variety in general. Lots of people like the game, but most of them wish it somehow had more.
Well, I guess that bodes well if I ever want to make a larger version of Lair! And I do, at some point - but I'll have to figure out how to make it work financially first.