Quark 2AA lights from 4Sevens are excellent and make very good bike lights (held on with TwoFish lockblock or even with bands made from spent tubes...). I like Quark's with *tactical* interface best for biking - you have a broad selection of levels that you can set, but then there are just the ones you've set, no unwanted levels that you must cycle through .
Having said that, I think the Shining Beam XM-L (or XPG) S-Mini flashlight is an even better bike light, but runs on 18650 batteries. Its got more light for longer and is as light or lighter,...basically a win, win, win. If going this route, it pays to get the better and more expensive 18650's, like the Redilast or Eagletac rebranded Panasonic 3100mah 18650 batteries (can run $16 to $20 per cell Vs. getting 2 cells for under $10 from DealExtreme ,...the expensive cells run longer and last longer and pay for themselves in the end...). Shining Beam has AA based lights that you could check out if it really is a must to use everyday batteries...,.