Thanks Jim, I have heard good things about them. I have already ordered another, though, and my B&H order shipped today. 
When I asked here and elsewhere, the one name that keeps popping up, is Newton flash brackets. So I did a bit of research, and it turns out that the bracket I'm looking for is one of these:
1) Di100FR
2) Di100FRVG
The only obvious difference between the Di100FR and the Di100FRVG is the fact that the Di100FRVG bracket is a little thinner at the bottom (only one layer of aluminium), where it protrudes from under the camera grip and it is located a little lower (when used in vertical orientation), so it allows better use of the vertical grip (for people with smaller hands, I guess), right?
BUT, the Di100FR allows you quick attachment/removal of the camera from the bracket, yes?...
... So...
...How much of an "obstacle" is the Di100FR when used in vertical orientation? That was the question...
After mulling it over, I've gone and ordered the Di100FRVG from B&H...
I think the convenience of being able to use the vertical grip relatively unimpeded will greatly outweigh the potential convenience of being to attach and remove the camera quickly - I can live with a tripod socket thread in those circumstances!
It's a love and hate relationship: I know the flash bracket will make my flash pix better (there's no disputing that...), but I still hate using them! If the Newton is anything like it seems, I should be reasonably happy... 