
I've never tried them myself, for much the same reasons as you say Mummgoth. The ones I've looked at just don't seem particularly robust or comfortable. That said, a friend of mine has one, I think the Citysport or something, and she raves about how light and easy to push it is and I think it was pretty cheap.
She's not a 'cheap' kind of person IYKWIM, she likes a bargain, but wouldn't put her baby in anything second rate. Her recommendation would be enough for me to take a look at it if I were in the market for a lightweight.