I'm having a lot of trouble deciding wether I love or hate this game. Spelunky was released for the XBLA on July 4th and I downloaded it last weekend and have spent a good amount of time playing it. The problem I have is that the game is VERY HARD. Sometimes it is to the point of being incredibly annoying.
Let me explain. The dungeons in Spelunky are random, so sometimes you have a comparatively easy time progressing. However, sometimes, it really feels like the game decided to cheat you. You might come through a door to be instantly exposed to a trap or shops will be inaccessible when they finally spawn. Although the game does get easier as you learn it secrets, it is heartbreaking to be on a good run and have it ruined by an overly-difficult random happening.
The upside to this is that every accomplishment you make feels earned. I've only made it to the 3rd level a couple times, there are four plus at least 3 secret levels, but I've had fun. Since the levels are random, there seems to be infinite replay value, if you enjoy it. I guess the secret to the game is to take it lightly. If you're too serious about it you will end up throwing the controller.