I can now comment on this light AND the fenix, as I now have one of each. There are more complete and exhaustive reviews on the forum, use the search.

The fenix, on turbo, is a bit brighter than the ultrafire. But it costs almost 3 times as much. That's the tradeoff. It would be cheaper and brighter to use two ultrafires rather than one fenix...but then factor in the extra batteries, maybe it's a wash.

To answer the above question, yes most of us use a lockblock. I also tried the "universal mount" from DX which is dirt cheap but the mount is parallel (I use it along the top of my quill stem).