Okay, I've been looking at the 50W model, and I don't think I like the placement of the up/down buttons...
If you fire with your finger, you'd have to hold it left-handed to avoid changing settings with your hand... and if you're predominantly right-handed, you'll be forced to fire it with your thumb
If I were designing it, I would have left the up/down buttons at the bottom, in-line with the firing button... or at the bottom in-general.