I've got 2 - the lightweight one:
and a slightly heavier one:
I've settled on using the heavier one. The increased power and flood makes a lot of difference.
I bought a helmet mount at the same time, but ended up just using the velcro straps from it, as they held the torch closer to the helmet, reducing the weighty feel.
I think it's absolutely perfect. One battery is always enough if you turn it off for the less technical bits.
Some links to the other bits and bobs:
(there are a few other batteries, but these have been great for me).