The switch has been rubbish on every torch I've owned with the exception of Cateye cycle lights.
Twiddle the torch head, switch it on and off repeatedly, shake the torch or slap it until it lights up again, tear the thing down and clean the contacts, the spring and the switch, look for corrosion, do all these things and marvel at how the hell, in this time of technology, I have managed to buy yet another useless ornament!
Torch switches!!! Arghh!!!
Been more than happy with Chinese Cree torches off eBay for less than a tenner. Actually really well made.