For those who have done the London Eye, did you think it was worthwhile? Also, it is a good idea to purchase tickets in advance (Fast Track, only 15 minute wait). Finally, what do you think is the best time of day to ride. I was thinking about dusk...Thanks for any advice!

We did it at sunset, had advance reservations .... I loved it. Yes, it is worthwhile IMHO, but then, I am easy to please.

Not a good idea to purchase in advance - as what you can see is weather dependent.

If you do book in advance do so on the day so you know what the weather is going to be really like.

If you want to fast-track it you could always try the Discovery flights which get you a guide to tell you what you are looking at and are cheaper than fast track BUT they are only offered for specific times of the day

And remember - London is further north than any US place outside Alaska (it's roughly the same latitude as Calgary) so sunset times vary from 4:00pm to 9:30pm depending on time of year - so between now & the middle of August you cannot get a sunset flight on the Eye

AlanRow's concerns about weather are appropriate. That aside, I would buy ahead of time - I bought the day before via the London Eye's web site. You get a 10% discount for advance booking.

Our booking last summer was at 5:00 or so, though I think it would have been more interesting to do it as night fell.

It was expensive (about the equivalent of $25 last summer) but well worth it.

http://www.londoneye.com/

I thought it was a great intro to the city - it was the first thing we did when we got there. It really helped me gauge the scope of the city and get a feel for the geography. Plus, it was just plain cool!!

In a shameless plug, can I just mention that from June London will have two eyes - there'll be one at Greenwich too (in the grounds of the Maritime College).

Absolutely do it. It is a delightful experience. I am petrified of heights but had no discomfort at all on the Eye. I saved it for our last day on the most recent trip. After a week of walking around London, it was more fun for my companion (a first time visitor) to have some familiarity with the landmarks.
We went on a Friday afternoon and our total wait was about twenty minutes.

depends on what you mean by "in advance". Before you get to London - not a good idea because as already mentioned, the Eye is definitely a weather-dependent activity.

But you can phone the booking office the day before, or the morning of, the day you want to do the Eye. Then you will have a chance to know what the weather is like.

And as alanRow says - in summer you won't have a dusk or nighttime ride.