I think this game is great, I don't know what everyone's complaining about. It was the first GameBoy game I bought, along with Pokemon Yellow.
The graphics may not be great compared with todays standards, and the soundtrack is quite annoying, but I listen to my Ipod while I play anyway.
The puzzles are really difficult and great fun, and I think the fact that the enemies move so quickly just makes it more challenging and fun.
It is annoying that you can't save, but if I'm stuck I can put my Game Boy on charge so that the batteries don't run out, and I can come back later.
The most difficult thing in this game is the Lantern of Sacred Light level. The blue monsters can really hurt you and there aren't many med kits in the level. But overall, this is a really fun and challenging game.