Oooh, this is very near me! I grew up round here and moved back a few years ago.
I have a 2 year old DS and another baby on the way, and we're very happy with the facilities close to where we live. We've got three different playgrounds all within walking distance, and Horfield Common and Badocks Wood are also nice places to be outside with our toddler. The Ardagh centre on the common has a lovely café and play facilities - you could look at their Facebook page to get an idea. There are loads of toddler groups nearby, at various places on Gloucester Road and at Horfield Parish Church and the Crafty Cow (great family pub).
Gloucester Road itself is great for shopping - the independent butchers and greengrocers are much better than the supermarkets, although there's a big tesco at Golden Hill too which is also handy. There are lots of nice, family friendly restaurants and cafés on Gloucester Road, too. Horfield Leisure Centre is very close to the hospital and has a pool which provides children's swimming lessons, and a decent council-run gym.
My DC are not at school age yet, but Horfield C of E seems like a nice, smallish and friendly primary school. I don't really know about Upper Horfield. The local state secondary school is Orchard School which used to be called Monks Park and had a reputation for being quite rough when I was younger, but I think has improved a lot now.
Drawbacks - the area directly around the hospital is quite noisy, with ambulances going past and you also get the air ambulance (helicopter) whirring about which can be noisy especially at night time. Like most of Bristol, parking can be a pain so if you drive I'd prioritise finding a house with off street parking.
Again like most of Bristol, house prices are getting a bit mad. The further you get towards Filton and the boundary with South Gloucestershire, the cheaper the houses are generally. There are nice houses over on that side, but they're further from the stuff like Gloucester Road and the common that I've mentioned above.