I don't get where this business about Sussex being bad architecturally comes from. It's not like its full of grim 70s grey concrete. The campus is basically a fairly open green space with reddish-brown brick buildings which are not too tall. The light dispersal on the campus is good so when the sun's out it gets everywhere which doesn't happen so much when you have a more compact site with taller buildings. I wouldn't say the buildings are anything special but I wouldn't say they were ugly and when I've been to Sussex campus it has felt quite a pleasant site, when you're at higher parts of it eg the library steps, you can see that you're surrounded by hills and it is basically in the middle of the Sussex Downs.
I think one of the forms of snobbery on TSR about buildings is that some students want old looking buildings, especially Oxbridge rejects who want to try and subconsciously recreate for themselves the feel of history of being in an Oxbridge college, which is why they like Durham and apply for that Castle accommodation there!
Overall I agree with the assessment of Sussex as being a bit underrated. Considering it seems to have a 'middle ranking' type reputation these days, there do seem to be a disproportionate number of Sussex alumni in politics and the media, traditionally very elitist fields, and also there are a lot of overseas business leaders who studied at Sussex, especially in developing countries, I think they have done a lot of scholarships and so on for students from developing countries.
Possibly one reason for this was that in its heyday Sussex did enjoy a high reputation as one of the academic big hitters. Both my parents got rejected from Sussex in the early 1970s, my Mum reckons back then it was seen as say Warwick is now, ie not one of the 'old school' but one that was more or less up at their level and that a lot of people applied to so it was hard to get in.
Back then it had a reputation for rebellion (not just the rentamob student protests you get now, big serious lobbying campaigns against apartheid and so on) so it was where all the academic Che Guevara types wanted to go to, if they wanted to avoid the establishment unis, especially as back then when there was no internet or TSR, people just read newspapers and heard radio reports and Brighton had this image of being a left wing haven of revolution and sex by the seaside.
It seems that for whatever reason, Sussex went into decline in the 1980s and 1990s but it seems to be climbing back up. So overall I think its a pretty good institution.