I've been meaning to try Boris' weird Olympic cable car thingy for a while, and I finally got round to it a few weeks ago. We dutifully queued, then joined six others in a car. The women we were travelling with were absolutely terrified. It was sort of funny. Here's what it looked like (the journey, not the fear):
The only off-putting thing about it is it's location. Obviously it was useful during the Olympics, but now you're essentially getting a cable car from a (probably) empty conference centre to a (perhaps) empty arena.
On the 'ExCeL' side, there is a weird exhibition about the environment... I don't really recommend it, unless you enjoy feeling scared witless about the future, in which case make your way over to the Mega Theatre. (I wish I was making this up). The O2 end has a lot more going for it, with a cinema and restaurants inside... And it's only a short bus ride to maritime Greenwich, which I thoroughly recommend.
Overall I'd say that, for the price, it's probably worth giving it a go if you're in the area (it's £3.20 for a single or £6 for a return journey on an Oyster card). Using Oyster also helps to skip some of the queues. Try and get in a car with someone who's terrified. It makes the whole thing much funnier. Well, funnier if you're the kind of person who takes a sick pleasure in other people's discomfort. I am totally that kind of person.