For less than £50 these are very hard to beat, advertised as 900 lumens but realistically there around 550-600 lumens, which is a hell of a lot and enough to ride off-road with at a respectable speed.
Lots of info about them to help you decide if you want to ‘risk’ them..
There were initally battery problem (poor sealing), but ppl report that they are much better now. You will though have to wait if you order them from DX, as the Hong Kong post service is running on overtime at the moment (talk of a month delivery time vs the normal 10 working days).
Lots of different variations are available from the same site eg:
Older bettery type – http://www.dealextreme.com/details.dx/sku.25149
But LED wise there all exactly the same.
They are also sold by many UK/ebay retails (Merlin included) for around double the price of the DX site, nowt wrong with this, as long as you understand you being charged upto double just because they are a UK retailer.
http://www.magicshineuk.co.uk
This is the latest type also sold by a UK retailer (though they are currently out of stock).