Lightroom 5: New spot removal painting source selection just dead wrong

You can press the forward-slash (/) key a few times to cycle through a handful of LR5's best guesses for the source location, and some of these may be nearby or otherwise better.

This is a tip I learned from watching Jack Davis's CreativeLive sessions late last week. It is also documented various other places, but if you don't know what you're looking for then it's easy to overlook.

That's a great tip and it will definitely help. I'm not surprised that it guesses wrong most of the time. I do get that it's a complex problem. But, its mostly unusable and sometimes seems to be very very wrong--- painting out dust in the sky and it grabs tree textures. Wha?

+1 vote: manual mode option - I can usually find the right spot quicker than Lr can.

There is a manual option. You need to Ctrl-click and drag.

Julianne Kost explains it in her latest retouch video (the old one was hilarious as an involuntary demo how annoying the hunting down of the automatic placements is).