I understand the marina, being a man made development with nil natural current flows, is subject to quite bad silting up. I suppose eventually that for house owners that means their gardens will get larger, and after all boats do make fantastic planters !
The marina silts up which just adds to the general feel of shabbiness compared to, say, Port Solent (where I live) or Hythe. Having said that, the location is fantastic being a short walk from Brighton.
I cannot really think of boating reasons but if looking for a colourful town with nightlife and a station for London and countryside etc seems to attract many. For pensioners the local bus service is good but the council is anti car I believe so roads are poor,full of cameras and fine traps for the unwary . Provided you are a keen cyclist perhaps with an electric bike then I suspect not a bad location for an urban students lifestyle. If looking for a London culture outside London has much to attract many. If looking for a boating base Eastbourne might be better.
It's ok but I find the marina 'village' now an enormous grey expanse which on all but perfect days is a bit 80's South of France for my liking. It just seems massively over developed. The town is ok for visiting but having visited more times than I can count, I enjoy the novelty of the occasional visit but as an every day prospect I think it would get me down eventually.