What a marvelous price for a stupendous 3G/HSPA "mobile broadband" USB stick. This was previously £79 on contract and goodness knows how much for PAYG.

Not a bad offer when you consider that the stick comes "pre-loaded" with 1GB of data which is the equivalent of a £15 top up.

Top ups themselves, as suggested above, are also £15 per GB which according to Vodafone represents :-
that's 30 hours surfing, 650 emails and dozens of downloads.
Its the usual "No contract. No monthly bill. No fuss." deal and because you're not in a contract you pay the premium for it (contract Mobile Broadband is £15 per 3GB). But this is probably no big deal for the low volume data user. Those with more serious aspirations need to look elsewhere than this offer.