I don't have many bad things to say about Trenched, but playing through, I feel like it's almost too easy, and I'm only playing solo. Perhaps it's just an innate sense of how to play tower defense, but it just doesn't feel that difficult, less so with more people. Much more enjoyable with a couple other people, but even easier.
I'm curious to see how DF handles post-release Trenched. I'm curious to see if they'll raise the level cap, what kind of loot they'll add and what kind of levels will come with it. I'm keeping my fingers crossed for some kind of survival mode. The biggest problem is that I never really feel like I am in any danger.