I was looking to book using BA miles a trip to Orlando, the taxes were quoted as £160ish. I could have got a return ticket on the same flight for about £309, so after spending £20k on my credit card to earn the points I was only recieving £150 discount, hardly worth it. In the end I have booked business class one way, ticket price £2,978 (I only had to pay £157 tax though)and booked Flyglobespan business class on my return $529.
At least I feel I have earned someting now, so am getting a business class round trip from GLA-Florida for £400ish, cant be bad.