I know the wording about the Citybus destinations on the leaflet you are talking about. I always thought that was normal. A good few routes in Dublin work like that as well. I presumed like Ciaran suggests that it's less work for the drivers when they get to the City Centre. Some cross-city linked routes are very close together on the Citybus destination blinds anyway, e.g. Mount Merrion via Botanic Avenue (85) and Carr's Glen via Oldpark (93) are right beside each other. If the buses all show 'City Centre' then you have to look more carefully at the route number to see what route it's taking to the City Centre but with various different destination names you can pick out your bus more quickly from a distance. Does it not work like this in England?
I wouldn't trust anyone less than an inspector to give me advice on which bus to take; all that most of the other staff do is read the timetable, which you can do yourself. The journey planner on the Translink website http://www.ulsterbus.co.uk/lowgraphic/entrypage.asp is quite good and can throw up interesting but efficient journey arrangements that you wouldn't have thought of. Sometimes doesn't work that well with Netscape though.
There *is* really quite a good Ulsterbus route map and it is mad that it isn't available on the Translink website but you can see it on my site at http://www.sjp.clara.net/nibus/ubserv.htm
The train journey from Derry to Coleraine is very nice out along the coast, preferable to sitting in a cramped Goldliner I would have thought.