I like the idea of knowing, at least vaguely, what I'm looking at but it doesn't seem like the discovery flight allows you to jump the line (sorry, "queue" alternatively, it doesn't seem like the fast-trak ticket includes the guided tour. Any thoughts?

There isn't a queue for boarding, only for tickets. Once you have your tickets, you are confirmed for a "flight" (boarding time) and you either get on it or you don't.

You can buy the tickets months in advance right up to departure time - just like on BA's flying machines.

Excellent, thank you Robespierre. Who spends 22.50, then, for the fast trak when 16.20 is all you need??

People that turn up at 6pm and have dinner or theatre reservations for 7.00pm...
There's often a queue for tickets but it's fast moving. You might not be able to buy tickets at 6pm for travel within the hour if it's busy but you could buy a fast trak ticket.

We did the tour with a guide because they offered a 10% discount when booking on line, so it came out the same and it was a smaller group. It was nice to hear the commentary even though we rode at the end of our week and were very familiar with all the sights. My husband had a nice view even from sitting on the bench in the middle. He does not like heights but we convinced him to ride. He liked everything, but being right at the edge of the compartment.

yes - if you are time sensitive fast trak makes sense.

The guidebook they give you w/ Fast track is very good - it is a glossy book w/ all the sites numbered on panoramic photos. Plus info about the construction/history of the Eye. You don't get this book w/ the Discovery ticket . . .

The book alone is worth about £7-£10.