There are two queues - the one to get your timed ticket, then the one to get on the Eye. You can avoid the first one by booking online and collecting the ticket straightaway. But you can't avoid the second (unless you are a special needs person or some sort of VIP). The trouble with booking online is you can't be sure what the weather will be like. The biggest queues in my limited experience occur from late morning when the average tourist yawns and turns out of his hotel. Personally I think the better views (weather permitting) are later in the afternoon when the sun is towards the SW and it illuminates the view towards the City.