Are Fast Track tickets worth it on the London Eye?

[Barbeasty]

We're going to London on a Sunday in June for DD's birthday. She specifically wants to go on the London Eye.

We should be getting into London before the Eye opens, but I'd rather not book a specific slot if I can help it because I either have to leave time in case the train is late in and risk hanging around or risk missing the slot if the train is late.

Is it worth paying the extra for Fast Track or are we likely to be wasting our money?

If you can then I would
Queues on a weekend are terribly long

Just thought I'd update in case anyone has this question another time.

We got to the Eye at around 10.16, so not long after it opened (although later than planned because, predictably there were train issues). There was already a long and growing queue at the normal entrance, whilst we were able to walk straight on having taken the advice and got fast track tickets.

Given this weekend had 30°C weather, I'm glad I took the advice and swallowed the extra cost.