I like having the app open when I'm on a run. I can hatch eggs, take a breather at gyms, and pick up a lot of Pokemon. Tracking was never an integral part of my game experience, which is maybe why I didn't feel as affected by the changes.
I never completely understood the complaints. Niantic has a right to make a (free-to-play!) game and don't owe us anything. And since this is a dev-centric community, many of us can appreciate how stressed out Niantic engineers probably are right now after a difficult launch. I get that maps were cool - I have a nice Dragonite to show for it, but it always felt like a hack that was going to go away. The old tracking system was better, but I'd rather have the performance of August than the tracking system of July.
Losing users was probably inevitable. This game was everywhere in the news, so I'm sure plenty of people tried it out and realized it wasn't for them. Combine that with people who miss their maps as well as maybe adjusting the numbers after catching bots, and that probably covers most of the numbers.