What amazes me when thinking about Gmail is how today's thunderbird (or evolution or whatever) are still miles away from the ease of use the old GMail UI had.
Local search is as slow and as bad as it was 20 years ago.
I use TBird. I believe there are two search mechanisms:
1) The "Search Messages" dialog that you get to from the menu Edit/Find/Search Messages... Can you say "slow"? I knew you could! I tried this just now, and it seems to be stuck "building a summary file for" one of my local folders.
2) The "Search" box that appears in the title bar. (What is it with scattering tools all around the outside of an app?) This is fast.
The advantage of (1) is that you can limit its search to particular locations, but you pay for that with sluggishness.
Thunderbird has access to all the mail locally in my case. POP3.
But I think this is on point, Google has the infrastructure to index that massive amount of data while my thunderbird still deals with mbox (I think) and can only index when it's running (and god forbids that indexing hogs up my celeron and my 3gb of RAM !).
I've been using thunderbird for years and I still find search to be bad. I've never really made experiments to see why it's bad, but often I type the name of a correspondant to find a particular message, but I don't find it.
I guess I am used to the fuzzy search magic that happens in other software.
Ctrl+Shift+F and "search all of the following" with multiple filter lines returns me what I need most of the times. It required switching my workflow though, yeah, the Google's fuzzy email search is really good.
Indeed, search in thunderbird is ok, but search in gmail is awesome. I started archiving my emails in folders and subfolders again once I stopped using gmail interface.
Local search is as slow and as bad as it was 20 years ago.
I am probably not doing it right though.