First off I couldnt beat the first level no matter how many retry's until I moved my gamertag and save data over to a USB 2GB flash drive. It appears the game could not save to my 250GB hard drive on an old model xbox.
2nd is that on each of the boss levels, no matter if I died on the boss or beat it without dying I could not progress on the first run. Its probably because if any achievements pop on a boss level the game will not let you go back to the lair. Also no matter what, I had to die on the boss in order to get the back to the lair screen.
The levels that didnt have a boss appeared to be ok and I only had to play them once. This game is SUPER easy but these glitches will prevent a ton of people from ever wanting to play this game.