Could have been great if not for frustrating and awful save system.
Turns out the joke was on me (and on anyone else who detests retracing his steps repeatedly), and a cruel joke it is: each time you die, you're sent back to the very beginning of the level, which can mean half an hour or more of going through the same motions. Again and again and again. I have no idea what those "saving" messages were all about.
Yes, I realize there are self-styled "hardcore" gamers out there who enjoy repeating the same actions ad nauseum until they get past a stopping point, but I am not one of them. (Of course, there are also masochists out there who enjoy beating themselves repeatedly on the head with a large mallet. I'm not one of those either.)
What a shame. If not for the frustration inherent in the sadistic save implementation, this could have been a great one. If only DS games could be patched like those on the 360 and PS3.
(FWIW, my ratings reflect my frustration with the save system more than anything else. The difficulty level of "very hard" is entirely due to the save system. If the game actually saved more regularly, I'd have rated it "just right." Similarly, I would have set the classification at "surprisingly good", and the score at maybe 7.5 or 8.0)