I use 'Applied Ballistics' app (cheap and simple) and a bog standard Kestrel for close wind and experience for down range wind. No problems so far. A little bit of pre-planning for G7 data (readily available). I've tried other apps and they all do roughly the same thing.
There's no substitute for developing your own dope, I keep a log book and irrespective of weather conditions ballistic settings for drop are usually close. For example I dialled my previous settings at my last Eskdalemuir outing in February and first shot hit at 1550 with .338LM. That'll do.
Elevation is physics and amenable to calculation however windage is part physics part black art. There's no substitute for developing the necessary wind-reading skills. Unfortunately field ranges like Eskdalemuir have next to no wind indicators - the best usually being your (or your mate's) last shots. I'm yet to see anyone achieve much with taking a wind reading at the firing point and nothing further for +1000yds!
With regard to Quick Load, I have just purchased a copy and find it useful when considering a new powder. Is it 'invaluable'? Not in my opinion. It's also only as good as the data you enter - I've just run some 5.56 simulations and the QL data for NATO brass and Sierra MK dimensions do not line up with actual measurements of components in hand so inputting one's own data is necessary.
By the way Ralph, are you going to the Stafford Classic Bike show on Saturday 20th ?