I have never felt more like cattle than when visiting the Eye. Once you enter the correct queue, you wind your way around to the front where you and about 20 others are prodded into a moving car. Once crammed in with far too many people, they slam and lock the doors behind you. If you’re lucky enough to stand next to one of the air vents, it’s actually a quite enjoyable ride. However, if you aren’t, it can get quite stuffy. The ride itself takes about half an hour and if you are easily bothered by small spaces and heights, this probably isn’t the best attraction for you. The eye offers some rather impressive views, but they tend to be obstructed by people or the other cars on the Ferris wheel.
Again, advanced purchase of tickets is highly recommended. We paid for the fast pass. It definitely saved us some time, but probably not worth the extra 10 pounds per person. My overall recommendation would be to opt for the views from the Shard over the Eye.