I used to use one of them, but only to screw on when checking my pressures. It felt a bit heavy to have flapping around on the move. I just run around on the rims now, saves my hands getting dirty checking tyre pressures.
Yes have used them in the past, have no effect at all on the wheels becuase they hardly weight anything. The do however mysteriously undo themselves in the bikeparks and then find new owners
Save you lots of trouble when pumping the wheels but have had problems checking the pressures with them.
Warning: I forgot to remove it from my rear wheel on a VFR750 and within 10 miles the tyre had started to deflate as the thing had come loose, flapped about and opened the valve.
They are great if you remember to remove them.
Nowadays I use a 12V compressor to check the tyres at home. About 15 quid from Argos. Plugs into an accessory socket. This has a small nozzle and flexible hose so that it fits all bikes without problems.
I use one of these but I keep it in the toolkit under the seat and never leave it permanently attached. I have found that as most garage forecourt air hoses are designed with car wheels in mind that using one of these is the only way I can easily get the nozzle to fit onto the valve.
A useful bit of kit but I don't think it was ever intended to be a permanent fixture as I would imagine it would upset the wheel balance.
You can get 90deg valves to actually replace the valves on your wheel, rather than bolt onto them. I think I saw them in the latest MPS catalogue - they've got a blue anodised finish. If anyone has the catalogue, perhaps they'd post details (threw my catalogue away)...
I´ve got them on my two wheel tractor. Bloody marvellous - it is near impossible to use garage air hoses on the back wheel - at least the Spanish ones. I can´t say I´ve noticed any negative effects.