I used one for a week over the summer when visiting relatives and found it really hard to steer - the front wheel seemed very stiff when DS was in it (he's 3 but not huge for his age). It was fine to push when he was walking though.
I really do still need a buggy for various reasons, ours is huge and cumbersome, there's one FS locally for peanuts and it does fit all my criteria otherwise so - are they really pants for heavier children or was the one I borrowed faulty?