I've been wondering about a set of them myself. Could you let us know what you think after trying them?
They're good!
I went for a ride today and got used to them almost immediately. No vibration, reasonable positioning, good visibility to rear, easy to adjust even on the move.
One thing I else I did do on getting back: They come with a selection of 1" high adapters in aluminium. I fitted the right one with the LH thread (the ram ball is RH only) and I found whilst riding that the extra inch gave it better visibility than the one on the left, which I'd gone without. So I fitted one to the left too. I also threadlocked all screws because, why not.
I'd previously used 50mm extenders to widen the stock RE mirrors, and that worked okay for lefty but right had a lot of vibration, as I had to get another LH-thread one which wasn't as good. Lefty also came loose the other day on a ride - no drama, and I had tools to sort it with me. I've never dropped this bike, but extenders and the original mirrors make them more vulnerable, whereas the doubeltakes are "unbreakable".
Are they worth £133? (UK price). Yes, probably. The quality is top notch. The mirrors have no distortion and the design is very good. On the basis that I can move these to other bikes if I want, they should be a good investment.