Yeap, the early 206s had quite a few problems, but nowadays they are mostly sorted out. The 307 is a nice car as well, my sister and a friend of mine have the 1.6 model and it is a very pretty and comfortable one, as well as safe. The first edition of 307 had a few s/w glitches affecting the steering wheel control system, called com2000 which consists of the wipers, lights, indicatiors stalks. Eventually these s/w problems have been rectified/solved with the facelifted model.... Any more info required???
The 107 is cooperation product between Pegeuot, Citroen (model C1), and Toyota (model Aygo). They share floor base, engines, gearboxes etc. It's a matter which style you prefer, though after seen some pictures the C1 is the coolest of all.