Got mine last week. Feline, red.
As many are commentating, this is a different car to the 107. So:-
General comfort and ambiance - much, much improved. Very good radio/stereo - when I have finished adding track numbers to all my MP3 file names it will be superb (grrr!). Seats better than 107, not a patch on my 2 GTis - but then maybe the less marked side bolsters won't collapse like on those!
Ride - well, Rennes cobbled/much dug up streets seem to be much less knobbly! A lot quieter over bumps and at speed.
Engine/gearbox. Yes, as reported elsewhere, the 1.2 unit is a bit rough on tick over, but this is already showing signs of diminishing with kilometres on the clock. Other than that, the increase in available power and particularly torque is very noticeable. One particular hill on a regular route, on which the 107 really used to run out of breath has now disappeared entirely! Engine note under load is of a more "growly" nature then the 107, which is much nicer. Oddly, gearing is almost identical to the 107, near as I can get, 3100 at true (GPS measured) 110 Kilometres/hr as opposed to 3000 for the 107. With the extra power available, this is what puts it in a different class driveability wise.
Not finding clutch engagement problems in stop/start traffic as some road testers have reported. OK, grab point is slightly different, but same goes for any different car to the one you are used to.
The agricultural gearbox whine of the 107 in 1st and second has gone entirely.
Lots of nice new toys to play with of course. I particularly like the speed limiter is much better than a "conventional" cruise control.
Overall - well, since 1987 I have had 2 205 1600 GTIs (non cat, then (rubbish!) cat, 2 206s and a 107. Not having much cause to use the rear seats, I reckon this is might come in be somewhere between the GTis in overall satisfaction.