I can speak collectively from myself and my housemates thoughts. Sussex freshers is hit and miss. The barn dance was fun, as was the welcome party which rocked! The thing about Sussex is, we have brighton right on our doorstep. So the partying simply doesn't really stop. Whereas at other universities (Warwick and nottingham I know for sure) they have wicked freshers because the nightlife in their cities is lacking. When I say there are loads of clubs or pubs and bars in brighton, there really is something for everyone. We all agreed in the end we found it a bit hit and miss because we have nights on at clubs every single day of the week.
Think of it as a trade off. You get a slightly lacking freshers, but a bloody amazing club and nightlife throughout the rest of your stay. (All night buses to the university is a massive perk too :P )