New iMac 27" bluetooth mouse freezing

I've just got a new 27" iMac (late 2012) and am having some nasty bluetooth problems. Firstly I'll say that the supplied Apple mouse works fine, but I'd rather not use it as the shape is really uncomfortable.

So I bought a Logitech M555b bluetooth mouse, and found that the pointer was horribly jerky. It freezes for a frame or two, then skips back to where it should be, and it does this at least once or twice a second. There's also masses of lag on the pointer, like it's always trying to catch up with my actual movement but never does. I've tried it with and without Logitech's drivers, and it's the same with both.

Putting it down to a dodgy or incompatible mouse, I then bought a Microsoft Sculpt Touch bluetooth mouse. It was an improvement, with no lag, but the frame skipping was still there. Microsoft don't make any Mac drivers for it, so it was just running as a standard bluetooth mouse.

Finally I bought a Wacom Intuos 4 bluetooth graphics tablet. Pointer motion with this is absolutely horrible. The pointer freezes for at least a couple of frames, then leaps forward to where it should be, and it does this 2-3 times a second. It's completely unusable. The Wacom can also work wired on USB, and when I do that, it works perfectly. This is with and without the Wacom drivers installed.

With three third party bluetooth devices not working the problem is obviously with my Mac, but as one final test I tried all of the devices on my old MacBook (running 10.6). All worked perfectly on bluetooth.

I called Apple and was told this was the first they had heard of it, but because the Apple mouse worked okay they put it down to 'incompatability problems'. Well to be incompatible with every third party bluetooth devices is obviously a massive problem. They couldn't provide a fix or any idea if one would ever happen, and just said I could return the machine for a refund.

So my question is, has anyone else tried third party pointing devices on a new 27" iMac (the new thin one), and how have they behaved? Is the mouse pointer as smooth as when using an Apple mouse? Or does it skip and freeze?

I only have a couple of days left to get a refund unfortunately, which would mean another Windows PC as I can't risk getting stuck with a computer with such a massive hardware/software bug.