I happened to start watching Slither last night. Sounded like another of the cheap horror flicks we're inundated with each year, but my curiosity was piqued by the inclusion of the always winning Nathan Fillon. Lo and behold, it's great! From the middle of the film forward I laughed more than at all the recent Will Farrell movies combined.
It doesn't hurt to have the context of the Evil Dead series here. This movie is in the "comedy horror" genre. Evil Dead gets it just right, but disappointing movies like Shaun of the Dead show that the recipe is hard to nail. The director here, James Gunn, has threaded the needle.
With some trepidation, I checked with Rotten Tomatoes, and what do you know, critics actually agree with me. It also has the advantage of being disliked by the perennial nitwits of the criticism world, both Ebert and Roeper---a huge plus for me.
So, if you liked Tremors or especially Evil Dead, give Slither a shot.