I agree with both Curtis and CDI.... you have to go to a store and actually handle one a bit, at least to check its build quality, how much it weighs, is it comfortable to hold, etc.
But basically, you want it to:
1. Enable you place the flash head above the top/center of the lens by AT LEAST another 4" or so.
2. Allow for some rotation of either the camera or flash,
3. Be comfortable,
4. Be somewhat balanced, and
5. Not shake, rattle, roll and otherwise fall apart, crimp or cut your off camera cables after a few uses.
For the price you want to pay though, you won't be looking at Custom or Newton, two of the top notch brackets out there.