That first enthusiast release of Windows 10 Mobile had just 'Slow' and 'Fast' rings, depending on how broken you were prepared to accept each new release, set against the promise of earlier access to new features and bug fixes. Then in February 2016, i.e. eight months ago, we had the introduction of a new Insiders 'ring', 'Release Preview', aimed at giving a stable experience for OS versions which were about to hit production devices.
So that's four different OS branches or versions that most people reading AAWP can choose for their smartphones. In fact, it's probably more, since there will have been quite a few people with older Snapdragon S4-based devices who left their devices in the Insiders programme even after Microsoft decided that the Windows 10 experience wasn't good enough on these older phones - such users will be left 'high and dry' on the last Windows 10 Mobile 'Threshold' version unless they also wanted to bite the bullet and experiment with the hack to get on the Redstone test branches.
Then you can add on people whose phones currently run Windows Phone 8.1 and are W10M-compatible but they haven't taken the plunge and taken advantage of the update yet (often because they didn't know about it). And probably some general users who upgraded to Windows 10 Mobile but who haven't been offered the 'Anniversary Update' (Redstone 1) yet.
Argh - that's a total of seven different camps/situations. And yes, that all sounds complicated, though for anyone who's been following along, through the ups and down, over the last 20 months, it's really not. However, a summary as of October 2016 and a recommendation is in order, I feel.
Assuming that you have one of the (fully) Windows 10 Mobile-compatible phones (everything in the yellow area in my chart), your main options then, all very realistic choices that you need to consider are:
This is the default condition for anyone buying a Lumia 950/XL, 650 or 550, or who did the official upgrade to Windows 10 Mobile through the 'Upgrade Advisor'. As it sounds, these are the most stable branches and versions of the OS, though also the least ambitious and with some longstanding annoyances still present. At the time of writing, the current build/release is on the Redstone 1 branch and is '14393.189'.
Then there are the Insiders rings. As of the Anniversary Update, you can find these built into the Settings/Update & Security pane, titled 'Windows Insider Programme'. It's simply a case of picking a ring and then sitting back and waiting for OS updates, though note that going 'backwards' from an Insiders release isn't always trivial (the advice varies from release to release and it also depends a lot on what you've got installed).
The idea behind this (newer) ring is that it's the one most enthusiasts 'should' be on (but see thoughts below), in that you get all the fixes that are heading for the production-status devices without having to wait for all the approvals and checks. Typically anyone on the 'Release Preview' ring will be getting future 'production' release candidates but a couple of weeks early. If you're in any doubt as to which ring is right for you and you're not into taking any risks, then go for this one.
The 'Slow' ring is currently in a strange place, since it's still tracking the Release Preview ring (as at October 6th 2016), but the idea is that this will jump very soon to providing 'Redstone 2' advance builds, at least those considered particularly trustworthy and stable. For my purposes, the 'Slow' ring sits halfway between the two extremes and has never appealed to me, but maybe it will be the natural home of someone who wants to be using Windows 10 'Redstone 2' but without a build every few weeks and without various 'known issues'?
Fast (and furious)
Ah, now we come to the most interesting 'ring' of all, and the point of this article. This is for (roughly) fortnightly builds of the next-generation branch of Windows 10, i.e. the next kernel, some new APIs and libraries, and so on. By definition, these builds should be more unstable and less useable than any of the other rings and versions, yet as you'll have seen from my rant last week, there are still significant issues in terms of usability once you start to really push the 'Release Preview'. So, given that you're going to have to work around and endure a smattering of issues anyway, why not do so with the most exciting Insiders ring?
But that's only half the matter, since we've been seeing more and more core Windows 10 UWP applications from Microsoft updated first for the 'Fast' ring, often with major new features (examples here, here and here) and only (weeks) afterwards pushed to people on production status smartphones.
Put the two together and for anyone with a passion for an evolving ecosystem and the Windows 10 UI, the 'Fast' ring is absolutely the place to be. We're now past the tricky 'early phase' of Redstone 2 availability, so it's safe to jump into the Insiders waters to this degree. True, not everything will work 100% of the time, but then a) 99% will work better and more smoothly than under Redstone 1/Anniversary Update, and b) the latter also couldn't guarantee that magical 100% stability either, so there's little to lose if you're still on the platform.
In my opinion - your comments welcome!