Brilliant in its simplicity. Can't wait for v2!
I have to admit, I was rather skeptical of something with the word "infinite" in it. But I LOVE it.
My comments (some of which will echo those that came before; sorry for any overlap):
1) Just a little bit of variety would help. A background that changes color as you go "down" -- or floors that are different colors. After a while, the b&w color scheme gets a little hard on the eyes.
2) It DOES get a little repetitive. I stopped at 1,000 because there wasn't anything compelling enough to keep me going. Any number of things could change that for the better: the possibility of multiple lives, with the speed ever increasing (which increases the likelihood of dying which makes the multiple lives necessary); different levels -- which means there's a goal to each one (x number of floors, or a power-up to grab that only comes up every so often -- if you miss it you need to go through x floors again before it comes up again); etc.
3) The power-ups/bonus items are difficult to differentiate, and sometimes impossible to reach. Again, some color here or shape/size change would help. Oh, and a short jump ability to reach those on the wrong side of the hole (but maybe that would be overcomplicating things).
BUT -- don't get me wrong, I'm not saying it should be some fancy light-flashing-über-graphics-heavy game -- just that the addition of a little (muted, even) color could go a long way. As I say, I'm really looking forward to the next version!