[dredmorbius]

It's worth noting that when G+ launched (oddly missing from your list), it didn't have search.

Even now, while G+ has search (and yes, it's both fast and comprehensive in that everything is indexed), it's missing tools -- you cannot search by author, by date, or by content type (posts vs. contents). Search is balkanized: you can search ... "pages" from the search bar (along with posts and content which is what you likely want), but to search a Community you've first got to navigate to it, then realize that the thing that doesn't look like a search dialog is actually a search dialog.

There's no negation (you can't exclude people or terms), you can't search by user, you can't search by date ranges.

All that said: search was the one thing G+ really had going for it.

[B-Con]

That's a good point.

It was missing from my list because I honestly never use G+ search and didn't know how to best assess it.

[dredmorbius]

I was pretty gobsmacked when it showed up missing.

For a while there, before Google's "you will be assimilated* policy really showed itself, Search was about the best thing about G+. I've since abandoned it largely for Reddit, which does have a featureful search, though it's not comprehensive (comments aren't indexed).