We booked in advance, taking advantage of a discou...

We booked in advance, taking advantage of a discounted ticket offer, which turned out to be just as well - not sure I'd be happy paying full price for the experience, which is rather corporate and sterile.
The queuing system works well, but the overall experience is fairly underwhelming. There are much better viewing opportunities available at the Tate Modern, which is completely free and doesn't involve looking through perspex, and St Paul's Cathedral's dome. Both of these allow you to walk right around and get a 360 degree view of the city, although admittedly St Paul's does require a fair bit of effort to climb.

Edited to add: further proof of the 'corporate and sterile' aspect of this attraction can be seen by the (presumably) automated reply below, thanking me for my "5* review".. this certainly is not a 5* review