The cable car over the Thames is great. The views are just as spectacular as the London Eye and it's much cheaper.
Yup I love it too and the best and cheapest way to travel is just to tap in and tap out, although they try to sell expensive tickets aimed at tourists.
But that doesn't mean it isn't a white elephant - it was supposed to be a genuine infrastructure project for commuters not just a tourist gimmick.
That said I have quite a lot to do with the TfL folk and they were delighted when the cablecar came in as it allowed them to claim they did all four transport modes - road (well obv buses, bike hire etc), rail (tube, DLR, overground), water (river buses and ferry) and finally air (the cable car!!). Bit contrived but it makes them happy.