Scunthorpe. My home town, and it was never a great place, but it's been declining and it's now just depressing. Walking through the centre is awful. As a teenager, all we did is drink and watch music, so there were enough pubs/venues for that.
Bracknell. I live there, despite vowing to not 20 years ago when I moved here for work. My GF found a house near the centre with a great garden and near some woods. So the house and proximity to the station are fine, but the town generally awful. Not been out for food/socially here for 15 years? Just go into Reading or Wokingham. (Apart from quick beers after work with people).
Luton/Dunstable whatever. My family are all from here, so went loads when I was younger and often go over for events. And it is depressing every time I go.
I think Swindon gets a lot of stick. It's grim in parts, but New Town is fine, and there are much worse places. Possibly my view is skwewed by the places above which all inform my outlook. I've lived in Swindon for a year and stayed there for work for 8 months and found it OK.