We went for a few days in February and the queues for the ET were horrendous even then. We eventually went up on our 3rd day but very early- just after it opened. We were staying in Paris so it was easier to do this. It was worth it. However remember there are loads of other lovely things to see and do in Paris so if the queues are too long just enjoy standing under the Tower looking up and as someone posted already the view down towards it from Trocadero is fantastic (and even better at night).
Someone has just posted a link to the batobus. Dont confuse this with the trips on the river with commentaries. We always get tickets for Batobus but it is what is says -a bus on the river. It can give you a chance to see some of Paris and gives your legs a rest but can take quite a while to get from one place to another. Look at the map carefully as it only stops at stops on one side of river and then other on way back. So if you want to go for example from Eiffel Tower to Louvre it can take over an hour. The tickets for this however are day tickets so do allow you to hop on and off which the trips on the other boats dont- they are trips with commentary.
We really enjoy going on the batobus when in Paris but it is not a quick option and if you want to get from one sight to another quicky then the metro is the best option, however you cant beat getting a good map and walking.