Clones, huh... I tried the demo, and it didn't appeal to me for whatever reason.
I actually never tried the demo version. It's different from Lemmings, I'd say. I do think (at least with the full version beta) the puzzles are more challenging than Lemmings and ONML, although in some cases not necessarily in good ways (a few puzzles just seem to be too much work to execute through, in the tedious sense). I think one of its appeals to me compare with Lemmings is that the game supports a richer variety of level objectives--even in singleplayer levels, you can have levels with win criteria other than getting to the exit. Also a good touch is the ample use of annotations and other verbal mechanisms that helps make playing a level a more engaging experience. Of course the graphics and music are much nicer, as are the capabilities supported by the level editor (maybe too much, as I find it an immense challenge to create decent levels in it compared with LemEdit/L2; but then again, the official levels in that game kinda set a high bar in terms of visuals).
But evaluating the singleplayer levels is kinda besides the point for that game. When you tried the demo version did you try multiplayer levels? I personally have not done any multiplayer sessions yet on Clones but I think it is what the game creators' are most interested in in terms of feedback.
The last thing I'd want is to start a challenge and end up having to do the whole thing myself 
Hmm. Huh, too bad, I was kinda counting you'd go that route.
You should start anyway, maybe with luck you'll get other people to pick up on it after posting a few initial results. If not, you can always leave it half-finished just like many of the other challenges on this board.
