Everything that we've tried so far: Nikon SB-600, Nikon SB-800, Nikon SB-900; Vivitar 285 & 283. The weight limit for "full horizontal extension" is, in our experience a tad over a pound. (Loaded with batteries, we have no problems at all supporting a SB900 on the Nasty Clamp. According to Ken Rockwell, the SB-900 is 18.655 oz. (528.7g) with 4 Sanyo Eneloop AAs. Nikon specs 14.6 oz. (415g), empty. (SB-800 is 12.3 oz. (350g), empty.) Of course, you can get away with more weight if you want to hang it down.

Anything a 3" Pony Clamp can. We've heard reports of branches, sinks, doors, window frames, chairs.

Yes, that's the one. It's the standard screw mount on most cameras (point and shoot), GPS units, portable audio recorders, etc.

Over time, use and handling of the flex-arm will give it a little bit of slop as dirt and oils work their way into the joints. A fast and easy way to bring stiffness back to the flex-arm is to wipe it thoroughly with 99% pure rubbing alchohol (not the 70% or 80%) and then letting it dry out

The flex-arm of the Nasty Clamp is completely modular, and can easily be shortened or lengthened. Just bear in mind that the longer the flex-arm, the less weight that it can hold without flopping over.