I was looking at the Cateye EL500 (the new Optitube thing) for a while but decided on the Nitehawk Emitter. The deciding factor, price. Nashbar had them on sale for $45 plus another review from some other rider that used it.
I use it on my commute back from work. My route has a lot of street lights but there are a few spots that get too dark and this light works just fine for this situation.