Yes, I'm going through a weird viewing order, having started watching Glee midway through season two. Still, I wanted to see how they set up the characters, so it felt right to jump back into season one and, wow, it's weird. They're all so young! It sounds stupid, but I honestly assumed they just were cast as 20-somethings, but some of them (Kurt and Quin in particular) seem much younger. I'm also assuming they started out deliberately singing poorly, though then Finn goes ahead and gives one of his best performances in episode one. The pilot is riddled with continuity errors (Rachel's dads, Pucks hair and attitude) but that's an artefact of the weird way TV is made in the States; though why it also seems to have been shot on mid-80s analogue film cameras I'm not sure, given it was made in the late 00s...
From the perspective of the main plot, the show does come out swinging in some big ways. The whole Quinn-pregnancy is handled well and leads to some excellent/devastating moments for her and Finn as characters, as is Kurt's whole arc (who is brilliant as ever), though I found the Kurt/Finn thing a little distasteful actually. It's interesting that even this early, Will treads a strange path between extremely nice teacher and douchebag creep that should probably never be allowed near other people, let alone children, but he (as he tends to) comes full circle. Plus the whole Terri baby thing is weird and just weird, so understandable that he's messed up a bit.
Overall, there's the beginnings of what would become a decent TV show here in the first season, and it's quite fun going back and seeing where all these characters came from, but man it took a little while to find its feet. I'm honestly a little surprised that it managed to become such a big hit when this is the starting point, but I'm glad it did. Though, to be honest, I ended up skipping around the season a fair bit, so I may have missed some of the better moments.