Has anybody used one of these or something similar?

http://www.cameragrip.co.uk/acatalog/joby_gorillapod_slr.html

if so, are they any good?

Cheers Scott

I use the little one for my compact and its great.

If you can wait, you can get them A LOT cheaper from Dealextreme

http://www.dealextreme.com/details.dx/sku.2332

I have one, ok for my point 'n' shoot but not tried it on my DSLR

I have one and think it's great!

Use it for timer shots, even hanging off the branch off a tree

I've got one of the ones designed for compacts, just about works with my camera which is somewhere in between slr and compact.
Its not had a lot of use, but its great for timer shots and for steadying the camera on things like long exposure shots!