Mine refills easily with either my track pump or my Topeak Road Morph pump, no leaking from the valve on mine as it can keep at full pressure all day.
The Road Morph and track pump can easily get to the 80 psi the horn needs to work at full blast, a locking lever on the pump heads keeps them from popping off at high pressures.
Regarding braking and using the Aizound, for me it isn't one or the other. I simply have it set up on the left hand side of the bars where my rear brake lever is situated. The rear brake is no use in an emergency stop as weight transfer will take all the weight off of the rear wheel and it will just skid under heavy braking. Likewise all the wight is put on the front wheel so I always brake from there when I need to slow down fast, this means I can have the left hand on the horn and the right hand on the drop or cross brake lever and have as much stopping power as I can get in any instance. I would only need to use the rear on a long descent to keep the rims cool or if there is a real chance of a front wheel skid (icey,snowy weather).
Although I can see the need to have both hands ready for the brakes, just use discretion in situations where you feel you may need it or where it is unsafe to use it (i.e use it when you need to let someone know you're there but not when heading for the bonnet of a car at full whack!)
