We had a very similar setup at our last house (also on a hill), although ours was a very wide garden (100') but not so deep. We were detached with one fairly close neighbour to the right, whilst the house (actually a 60s bungalow) on the left was not visible from ours at all.
Behind our garden we had five (far newer, ours was Victorian) houses with much smaller gardens all backing onto ours. Theirs were probably around 20-30' deep and obviously fairly narrow. They were also built into the hill so that the part of their gardens closest to ours were higher than their houses.
Three of the houses had families with youngish kids, two of which had trampolines right up against our 6' fence (which we'd installed as previously there was just a wire fence along the whole rear of the garden). One family built a summerhouse adjacent to the fence and their kids would regularly jump from the roof onto the trampoline. They would also stand on the roof, peering into our garden and setting off our two dogs barking. When we attempted to install trellis to grow climbers above the fence two neighbours complained and we abandoned the plan as by then we'd decided to sell and didn't want a dispute we'd have to declare.
We sold up and moved more rurally - the old place was a village that had been encircled by new build estates- and now have just one near neighbour....
But - our one neighbour is a twat, a local 'mansion' has occasional weddings which can be noisy, it's chainsaw and quadbike heaven, plus there's a nearby dog kennels which when the wind is in the right (or wrong!) direction you can hear in our garden. Also lots of shooting wildlife on Sundays.
So, in hindsight I'd actually rather have stayed where we were!
Every situation is different though and good neighbours now doesn't necessarily mean they'll stay good forever. I do agree that the more houses/gardens that back onto 'yours', the more likelihood there is of issues going forward. Its just so hard to make the decision.