I live in West Norwood and have done so for 16 years now. The place has improved massively in that time, and greatly so I would say in the last 5 years.
People have been priced out of the surrounding 'gentrified' spots surrounding it (West Dulwich, Crystal Palace, Herne Hill), and so it was only a matter of time before things improved and prices have shot up accordingly. It still retains a bit of a diverse edge to it too which I like (not yummy mummysville like East Dulwuch for example), but you can definitely see more money moving into the area.
The high street is a bit poor, but there is a new leisure centre, a number of nice coffee shops, a Blackbird Bakery and a decent family friendly pub there now.
More openings/improvements planned too, so definitely an area on the up. There is also the monthly 'West Norwood Feast' which is a community led day with stalls, lots of foodie stuff, vintage clothes and bric-a-brac stalls which is definitely worth a visit.
I agree that roads near St Julians Farm, Thornlaw, Casewick, Lamberhurst, Thurlby are nicer. The area's more towards Gipsy Hill I don't personally like as much.
You can get into Victoria or London Bridge in about 20 mins, so good rail connections, and there are some great primary schools in the area too.