Having lived in Brighton & Hove for my whole life, I can say that it's really nice. It is mainly students in Brighton, but then if you go to Worthing or Shoreham then you start to see a load of old people!
Not a fan of the beach though, a pebble beach is awful! So painful walking barefoot on the beach as well as tiring.
Nightlife is quite good, though it starts to get a bit repetitive. Brighton Wheel has just gone up as well, looks quite cool. Need to give that a shot!
I don't actually know anyone who has generations of family from Sussex. Most people in my experience have parents from London, or from Scotland, Ireland, Germany, France etc.