I've used RAM cradles and arms/brackets with both my Garmin GPS45 and GPSII+ over fast and rugged terrain (Morocco, Spain and UK) and would echo the comments above - great quality (and value), but the cradle can mark the GPS casing slightly (I lined the cradle lips with gaff tape to help protect the casing, and make the fit really snug); and you need to nip the screw on the RAM arm up nice and tight to stop it coming loose, but yes, the rubber coating on the balls does help take the shock out. They work great!
I've also been using a RAM arm with my new Garmin 2610 together with the Garmin (plastic) cradle, but unfortunately because of the way it clips to the GPS, the pins on the adjustable back plate of the GPS unit itself have broken... however, I believe the RAM 2610 cradle fits around the case more completely (similar to the others) so this wouldn't happen?
As for the comments at the top, I too tried the Touratech MvG mount with my 2610, and it was excellent up to about 50mph, then it started to vibrate like a mad thing and you couldn't read the screen info... I 'd still like to give their standard version ago to see if it doesn't vibrate as much as it does hold the GPS very snugly, and at the same time doesn't seem to mark the casing, but I'd say RAM is the most cost effective way to go...