Significant "Cloud" Improvement: Nested Labels in Gmail

I've meant for several weeks to close the circle on the biggest change in my own computing life in many years. This is my shift to virtually all-cloud operation, as prefigured here. Full chronicling some other time. Symptoms of the shift are: I haven't loaded Outlook in nearly two months, after moving my old PST files into Gmail*; and I haven't thought about which of my computers had the "current" version of a file, or copied files from one to another, in about as long.

The two indispensable enablers of this change have been:

  - The marvelous and utterly reliable SugarSync, which means I can get any of my files from any device, whether netbook or laptop or desktop or mobile phone, while also knowing that the files are all safely backed up. For later, why I think this is better and more flexible than alternatives like DropBox, and how to make it work with Mac programs like Scrivener and DevonThink, whose files are tricky to sync.

 - Gmail rather than Outlook as the ultimate repository for my mail, which I can then get at, via IMAP connection, from any of my computers in a variety of ways. I can use Thunderbird, Apple Mail, Outlook if I want, normal online Gmail on the web, offline Gmail via Google Gears (details and quirks of offline use later). No matter how I get at them, the messages themselves show up in the right classifications -- still-to-be-answered, nagging-but-never-will-be-answered, archived, etc -- from any machine.

About a month ago SugarSync announced a major new feature (details here), which I meant to mention at the time. I am piping up now because Gmail has just introduced a significant improvement: "Nested Labels," which allow you to create a sophisticated organizational structure in the vast swamp of info that is your Gmail message repository. Information here; illustration below.
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Often there is no point to "organizing" messages; you just assume that you can search for what you want when you want it. But at other times it's handy to classify some info, and at those times labels are far superior to "folders," since a single item can have many different labels.** The nested, or hierarchical, label system is one more step toward Gmail's being a main base of one's computing life, a la Outlook of yesteryear for me. More later, but that's the news for now.
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* Yes, I retain all the PST files for backup. The difference is that I don't have to re-archive them every day, because of Outlook's habit of marking a PST archive file as "changed" every time it's opened under Outlook, even if not a single byte is different.

** The combination of IMAP and Labels is slightly odd, in that IMAP systems seem to create a duplicate mail item for each Label a message is assigned to. This is theoretically inelegant but in practice it works fine. Labels are the way to go. Again more later.