Upload & Sell: Off
The OP was written in 2008 -- still the same decision, the same choice between gimbals exists. I did not find many other alternatives without going up significantly in price. I am sure the Wimberleys are really well made, superior products, and I appreciate that they are manufactured in the US.
There is a price for quality though. Instead of one of the top brands, I bought the cheap chinease  alternative, the Beike BK-45 on the *Bay. It cost about 1/6 of the price of the WH200 @ a top NYC mail order outfit, B&H (BTW, I priced both on 2013.02.10). B&H carries the WH200 for $594.90 + free shipping in the US. I paid $97.00 with free shipping from some *Bay vendor, you can find a similar price pretty easily I'd guess, but it would pay to look elsewhere: just reading reviews to ease post purchase anxiety, I found it online for US$70.00 + ~$13.00 shipping, so a few dollars cheaper.
Part in hand, I mounted my trusty Nikkor 500mm ƒ4.0 P with TC1.4 and set up to shoot the bird feeder from the living room (meh). I noticed immediately that I was getting too much movement at 1/60" to get a sharp photo. Is it the gimbal? I checked all lock knobs, they are tight, no noticeable movement. The lens is mounted on a 3" Arca Swiss type plate mounted on the foot of the 500, it shows no flex or movement and neither it nor the lens foot has never been an issue. I screwed the gimbal firmly to my (previously) trusty Gitzo GT2530EX. I believe the tripod flexes too much for the D3 + 500 ƒ4 P + gimbal combination, so the vibration would be the same issue with a much more expensive part: the tripod is just beyond its capacity to resist the torquing forces to remain stable. I'm confident the tripod would hold much more weight (*like my RB SD + 180mm + SD back or 8x10 Ansco with 19" brass lens.)
So the upshot is that the gimbal seems to be a good buy. The grippy coating probably also insulates the metal well. I would prefer large, rubber coated, round locking knobs for the 4 adjustments, but the two most commonly used knobs, to lock swing and rotate seem to work well (2" x 6 lobe and 1.5" x 5 lobe, respectively). The mount plate lock is round with a ribbed-rubber ring, and a pretty standard size. It works well. I take the most issue with the rise/fall lock knob (~1 3/8" x 2 lobe). This adjustment hold the camera + lens at a given height, bearing their entire weight, but it is bit hard to lock/unlock when you have to really apply enough clamping force to hold for certain. This is not a deal-breaker though.
Second real problem with the gimbal itself is mentioned in the OP: the distance to the center of the mount clamp from the swing arm -- about 58mm. This is a cm or two too small to mount my D3 (pro-level body) directly on the gimbal.
The BK45 seems like a pretty good effort, I imagine it will work as intended when I get my tripod issues sorted: looking at a Series 5 leg set, see if that works to kill the vibration. I think for the money it would be hard to beat.