When you use the detailed search in Gmail/Mailplane, it really is quite good. Better that Mail.app search.
Mailplane still has its quirks (especially about attachments), but I've gotten really fond of it. And their support is nice. Meanwhile Gmail for Mail.app remains unreliable.
I don't know what to do about my Sunday students though. A few have Gmail accounts and since it's Mavericks it's just not working well for them. I hate to tell them they have to buy a $25 mail app (or use the web all the time) just to get reliable mail. Even the $2 Airmail app has too many bugs to recommend it.
I suppose they could always use Thunderbird, which also works. Or just Gmail on the web, with the web limitation. Still, it's too bad Mail.app is left like this.
I actually called AppleCare about it, since I have a new MBP and tried to get it to work with a brand new installation. But after the initial sync, which does work, new mail simply is not coming in. AppleCare apologized and said they know about the problem and are still looking into it. And they confirmed my settings, but don't know why it doesn't work.
Apple basically took an app that was working and break it though. I think most everybody would be happy if they simply reverted to Mountain Lion Mail.app.
doug