we just moved to HOP in August, in large part because of the better-value house prices (we were in ED/Peckham Rye) and the excellent schools. The HOP schools do seem to be a cut above some of the FH ones (no offense) and I like the quieter, neighbourhood feel. That said, i was also very keen on the area around Sydenham Hill and Eliot Bank school, but the good houses seemed to be snapped up quickly. HOP transport links are good, and there's also Crofton Park, on the Thameslink line.
The downside is that there aren't any big parks on your doorstep in many parts of the area - so we tend to drive back over the hill to go to Peckham Rye Park. Dulwich Park isn't too far either, but not walking distance.
Blythe Hill Fields is fantastic though for the playground and general running around with children.
I see most of what I've written has already been said but I do think HOP is a great option for young families, and only bound to get better as more move in.