I know this is way off topic but why was the tram network never extended?
Politics.
Labour (nationally) were very risk-averse at letting cities building/extending tram networks.
There are clear areas where the Sheffield system could be extended, but the fact that the system had some design flaws (Herdings Park/ Malin Bridge branches) and some "bad luck" (high density housing areas that the tram was designed to run past were knocked down (Norfolk Park, Kelvin Flats) which meant it took a long time (and the introduction of Stagecoach) before they reached the initial "target" of (IIRC) fifteen million passenger journeys a year.
Then again, it was always going to be hard to estimate what the passenger numbers would be, unlike Manchester, as there was no existing rail market that the trams were replacing (whereas the Mancunians could use the existing volume of train passengers to Altricham/ Bury as a benchmark).
I think that as it links now both Westfields, and running up to the Olympics, LO will get even more exposure
Agreed.
Is there any scope for enhanced capacity though? AIUI the NLL is pretty much at capacity (due to freight), so is there scope for extending the 378s?
They do feel safe, which is amazing given what ran on there before (where I was always uncomfortable)
I've noticed that. I wondered whether it was because the design means (assuming that you are sat down) that you are never with your back to anyone, so you don't have to worry about what is going on behind your shoulder?
Plus increased passenger volumes mean passengers are less likely to feel isolated - anti social behaviour is much easier when there are only a handful of people on board.
The 378s are better than I expected them to be; they have grown on me.