I'm running:
WinXP SP2
2.40 GHz
768 MB RAM
Radeon 9550
It's running pretty bad on the lowest settings

I've been trying to play Ninja Mono, and I sometimes have to press left or right up to three times before it's recognised. If I'm trying to get from the left hand to the right hand column by tapping right twice, it might get into the center, if I'm lucky. It means I can never get the block things if they're bouncing backwards and forth.
I tried using the mouse, but that felt awful for dodging, and I'd rather not use a mouse if possible.
This is really annoying, because I love the concept. In the full version will there be a way to turn the graphics down more? I mean, a game based around three columns of blocks coming towards you shouldn't really be too taxing. I don't care about the fancy effects, I just want to play the game, and a game based around fast reflexes has got to be extremely responsive, and this game ain't.
The resolution settings don't seem to work very well for me. they either keep instantly setting back (I tried to run it in 640*480 windowed and it set it back to default) or cancelling selections (I turned off something in the options menu, forgot what it was. one of those tickboxes, 'disable ..." then an acronym or something that I didn't recognise. I turned it off in case it would help, but when I opened the window again it was deselected).
I don't want to buy it unless I'm assured the full version will run at an appropriate speed and respond accurately and quickly

It seems to run smooth enough, I guess. It's just the bad responsiveness that gets me.
It's fun though! and a great concept. I just wish it ran better.