BTW, I got mine for $13 ;p on the "returns" table at Nashbar when they still had a outlet store near Youngstown, Ohio.
The Century bars, as John mentioned, don't have flip-up armrests so you can't put your hands on the bar tops anywhere near the stem. For me, this is not a minor disadvantage. If I were riding with aero bars all the time, I'd spend the extra money for a set that had flip-up armrests.
I made a mount for my cyclometer by zip-tying a short piece of 3/4" PVC pipe between the bar extensions and building up the diameter to 26 mm with electrical tape. It cost nearly nothing and is plenty secure for the cyclometer. I don't think it would hold a headlight adequately and your arms would interfere with the light beam anyway. An underbar light mount is probably the only thing that will work.
One other thing about aero bars, the extra weight out front makes the steering more touchy. No-hands riding is difficult which indicates you have to be more attentive under normal circumstances. They require some getting used to before riding on them is comfortable and gusty sidewinds can be a problem. Like everything they have their upside and disadvantages.