I'm surprised people are saying it won't go as fast as the fiesta down the lanes as I know for fact that my RS would beat my old fiesta down the lanes....easily
Even round tight corners, it feels bigger but has so much more grip than the fiesta ever did, you'd come off the roundabout with understeer but in the RS its happy to do the same speed and wants more
I have considered swapping to the ST though just for the comfort side of it but now I know I wouldn't/couldn't
Don't know if your into it but the tuning potential is pretty good for the ST and not very expensive I believe, was looking at a blue one today and I think its now my favourite colour out of them all, even above the orange!

In answer to the question of fun...I reckon yes but not for the lanes, just the power of it