A great concept of a game carefully crafted and bundled into an easily set up multiplayer game. There is character progression, adversity which shifts constantly as other players take the role of the hero and the others take the role of the monsters trying to turn him into floor paste and some great bosses which allow for some nice action.
Overall, a solid concept. Now the reason for the no recommendation;
I played local multiplayer with a bot or two (not having more than one other person immediately available) and the result was a frantic scrabble after the AI, trying to figure out what to do. This itself did not take long, but the frantic scrabble continued on and on and on. Normally, frantic in a game is good, but this just felt like always playing catch-up and never progressing. At the end of each floor, regardless of character advancement, it always felt like we were not quite sure what had been achieved, what happened or what we were even trying to do. We continued on for a while, had a few boss encounters and played as both the monsters and hero a few times each. It was around the time my friend said "I'm bored" that I realized that I was too and had just been forcing fun onto the session.
The ghost characters constantly felt like they were dragged from room to room, rather than chasing the hero, often never having the chance to even attempt the various awesome traps in the corridoors between some of the rooms. The blob drops were a nice touch, enabling the ghosts to stay in the action, but not overwhelm the hero too much with mobs. But it still felt a bit bland and it was hard to relate to any of the characters with the constant control switch (mostly with the AI bots getting in there 9 times in 10). Overall, for two of us playing with two bots, it was not fun.
Other people with three friends to play with may very well have an awesome time with Crawl, but I think it needs a little more balance, maybe some humor or something, anything to bring it to life. Players need something to work with to get fun out of a game. Other than that, the devs have done an awesome job (love the boss intros, they looked awesome!) and I hope I get chance to have fun with this in the future.