I think that too: the game is repetitive, but it still has a lot of secrets (here's a guide of the game I just updated here: Hints.zip
). The main problem is that there's no scripting (or very few) or code-driven puzzles (as opposed to Gods, Cadaver or Chaos Engine) which limits the way secrets could be inserted. The secrets rely on some specific items (magic ball, chalices) and teleport rooms.
By studying the game, I found more secrets, like for instance the way to warp from world 4 back to world 1 and keep your score, allowing you to reach a huge score without completing the game. I also found useless items such as chalices in teleport rooms, which have no effect.
IMHO the most sedate level is the jungle level with growing plants. And the gamemaps are huge, in fact maybe too huge.
Apart from that, the programming is awesome, and the game engine is a little jewel. I still think this game is very good, and underrated.