Windows is far worse. They don't have a native PDF search facility (at least on Windows 7) and its sloooow.
iOS, I agree. It's gotten better, but the app search thing is bizarre -- especially since it works so well on Mac.
Edit: Sorry meant to reply to root.
I've never noticed my Spotlight indexing, except for when I've upgraded the OS. Items also come up very easily for me. I mostly use it to launch apps and it finds those for me with very few keystrokes. Maybe 1-2 gets me to the apps I use the most. For documents, it works well for me too, but not as good as the apps.
You can always try https://www.alfredapp.com/, but even in their blog they admit that with Yosemite kinda changed the game for them.
I use Spotlight religiously for the very reason that it's lightning fast for me. I've never had it index anything for me where it interrupted me even with multiple HDDs plugged into the Mac. Most of the time it only indexes after OS upgrades and I usually do those at night when it's not business critical. Same with iOS. I've never had issues.
Have you tried manually removing the index and then re-enabling it?
I also use iOS search a lot and haven't run into the problems you describe. The iOS App Store? I'm on the same page as you. It's totally frustrating and doesn't work right.
I have never had this problem, not even once. I love the iOS spotlight search.