i don't buy it.
at present i can't afford to, in general.
in the future, with an income (i'm a student), i would definitely consider it.
my dissertation is based upon the subject of sustainable agriculture (although with a UK bias), and therefore the fairtrade topic comes up. in theory i agree with it, one of the biggest difficulties for farmers, esp in the developing world, is getting a fair price for their goods. the ethos behind fairtrade is, therefore imo, a good one.
i guess i contradict myself in some ways though, as i tend not to buy fairtrade bananas - ime they are not as good quality as others. i'm not a coffee drinker.
what i have noticed (although not on here) is that fairtrade frequently gets associated with organic. which it shouldn't do. the research i've done on this shows positivity for fairtrade, and a lot of negativity (within the agri/food supply industry) towards organic ("organics? well they've a great marketing team...!")
i would be interested, though, on hearing what the fairtrade organisations views on organics are though...