Hmmmm,ive had a love/loath feeling about a few....
the verve,i loved it,but the creak is unbearable and DD stuck her feet out the basket and put her feet square on the ground
and DS put his hand under the wheel guards a few times 
the mima kobi,i loved the manuvorability and im SO glad i tried it,but it was a bit too beautiful for me,and i was terrified of ruining it
plus,it was a pain to sell.
then there was the p&t explorer, i just hated that,it was awful ...i cant think of a single redeeming feature.
the Luna mix (was 3 years ago,but im still going to mention it) was TERRIBLE,i hated it right away,i cant even start,EVERYTHING about that damn thing is awful,but i put up with it for months before i found the vigour (lovely)
and finally,the Vista: if everyone bought a vista from birth,i dont think there would be nearly as many buggy addicts. the only thing i can think of,is that the crotch strap is a little short (with my buggysnuggle AND sheepskin on)
but thats IT,and that is impressive 

okay,so that was more than one each wasnt it