My review, first the negatives. Please don't make a game with right-handed movement only, or even as a default. Please don't make a game with music that doesn't have a mute button.
The positives: I guess this is the best game of 2010, even though it's only 10 minutes long. I'm not sure what would be better, but certainly not an FPS with an RPG ladder. With Specter Spelunker Shrinks, we get a glimpse at an experimental mechanic that really does work, so that's a rare thing. Anyway, I had the shrink/grow mechanic in mind as well for a platform game, but the difference between Ken Grafals and me is that he actually executed the idea. This game is basically a prototype that's a proof of concept of the idea that vastly shrinking and growing on-the-fly makes for fun gameplay. Verdict: concept proven.
I actually think this mechanic itself is, ironically, part of a larger possible idea. Dear Ken: would you like to make the next Portal / Braid together? Not a joke.