I ran an engine match between Stockfish and Critter on my old 32-bit laptop. Stockfish won the match, but Critter won the first game in a model demonstration of a central pawn majority in the QG exchange variation. This was the best game of the match, although marred by Black's aimless shuffling with the king and knights. Critter's play however appears very "human" and strategically clear.
Style-wise I find that Critter plays like Topalov and seemed to sac an exchange in virtually every other game. Critter finds much more dynamic compensation than Stockfish, making Critter extremely useful for analysis. I am also impressed with both engines for their efficient use of system resources. Stockfish uses in general half as much RAM as Houdini, and Critter uses half as much RAM as Stockfish. Additionally, on both of my computers (old/XP and new/Windows7), Houdini continues to throttle the CPU at 100% if the GUI is closed while the engine is running. Because of this I have actually removed Houdini from my computers.