I just tried it, and it's pretty fun. My favourite moment so far was when I headbutted a dude's head
clean off.
I agree that I probably wouldn't part with $20 for it, especially in this economy and with my own current financial circumstances. At least not unless it was a super-duper-polished version (i.e. arenas that look like places instead of textured spheres, player models that look like...say, ninjas, fancier menus etc.) There was a graphical issue: all text in the menus and in-game was gray and almost totally transparent, making it hard to read. I'm on a 17" PowerBook G4 with 1.5GHz proc, 1 GB RAM and an ATI Mobility Radeon 9700 card. Judging from the YouTube video's fiery orange text, I assume it's an issue with my particular card.
I also found that, while cool at first, the nearly constant time-warping made the game difficult to play, frequently making me wait until it was finished "showcasing" one move or another before I could get on with it. It might be a good idea to tone that down a great deal, but add an option in the game's preferences to crank the time-warping back up (for example, if you want to show off to other people or record a video of how awesome you are). Reining in on the slow-down effects would allow players to stay engaged in the "flow" of their fight without being momentarily taken out of it by a random 360º spin and then thrust back in although such a potentially dramatic camera move might still be good for finishing moves.
My general feeling about Rubber Ninjas is that it's the framework of a really cool game, just waiting to have its AAA polish applied. I can imagine playing a round of RN with humanlike or cartoonish player models, set in a dojo...the camera zooms in to show the steely concentration on each player's face...
(Artist's impression)
...then they fly at each other at lightning speed, flailing in mid-air, music pumping (I'll admit I'm listening to the second part of Mona Lisa Overdrive here), time
subtly slowing to emphasize the most devastating moves as the blood and sparks fly! I think if you hooked up with a few good artists and modelers, you could achieve something really impressive based on this game. As of now, it still leaves the player wondering if it's quite finished or still a work in progress. In any case, excellent work!