The expected 'Release To Manufacturing' build of Windows 10 Mobile (i.e. being flashed into the first batches of Lumia 550, 950 and 950 XL), build 10586.11 is now available to all the brave souls (like us) on the Microsoft Insiders Programme. Details and a few suggestions below.

Having recently gone through the 'new user' experience with Windows 10 Mobile, you can take this one step further if you like, by doing this for the new Insiders build, 10586.11, available now on the 'fast' ring, since this is the build that's almost certainly going to be in the Lumia 950 and 950 XL when they appear in shops in the USA this week. In other words, upgrade to 10586 and then factory reset (and resist the temptation to 'restore' from a backup) and you'll be in 950 retail land (though slower!) Or you could just be sensible and upgrade in-place as normal and save yourself hours...

In order to make sure you get the new build, check that you're still provisioned for updates by going into the Windows Insider application and re-selecting 'Fast ring' and re-accepting the terms and conditions.

From the Microsoft announcement post:

Today we are releasing Windows 10 Mobile Insider Preview Build 10586 to Windows Insiders in the Fast ring. This build for mobile has a lots of good bug fixes and general improvements for you to check out. Overall this is a really great build, and we’re excited to get it out there for all of you to try. There is an important note for anyone who installed Build 10581 and then subsequently factory reset your phone, so please make sure to check out the known issues below.

• We have fixed the issue that caused the Start experience to become corrupted (garbled) after upgrading and restoring a backup from a phone that had a different resolution.
• You should now be able to set your default save locations via Settings > System > Storage and it will correctly reflect the current storage settings. Your SD card should no longer show up as a garbled name in Storage settings either.
• Moving apps to a SD card should no longer cause those apps to crash.
• We’ve made improvements to the Messaging + Skype app – through both app updates via the Store and also on the server side.
• This should be seeing less resuming/loading text when switching apps.
• The physical camera button should be working again if it wasn’t working for you before.
• Apps and games should download from the Store more reliably.

As usual there are some known issues, but the first one is major, so I'll include the list this time round:

• After we released Build 10581 to Windows Insiders in the Fast ring, we discovered a bug in the build that will cause the filesystem to become partially corrupted after doing a factory reset. For those of you who did a factory reset of your phone, you most likely did not notice this issue on Build 10581. Due to this bug however, upgrading to Build 10586 will cause your phone to go into a reboot loop after the upgrade completes – rebooting at the Windows or operator logo. To recover your phone, you can use the hardware key combination (quoted below) to reset your phone which will then put it at the OOBE experience on Build 10586. We highly recommend that you make sure you do a backup your phone *before* upgrading to Build 10586 due to this bug. Additionally, you can also recover your phone by using the Windows Device Recovery Tool to go back to Windows Phone 8.1 and then upgrade to Build 10586.
• Deploying Silverlight apps through Visual Studio to your phone still won’t work in this build. This issue will be fixed with the release of Visual Studio 2015 Update 1 on Nov. 30th. You can deploy UWP apps to your phone without any issues.
• There is a known issue where the tile for Insider Hub still remains under All apps but doesn’t open. Insider Hub isn’t included in this build. There isn’t a way to get it back unfortunately. However, it’ll return in a future flight! In the meantime, use Insider Hub on the PC as a workaround.

You should be able to upgrade in place, but - as ever - if anything seems out of place (especially if you did a factory reset like I did under 10581!) then it's always worth either hard resetting and restoring or, as hinted above, going for the full 'new' experience and rebuilding as if starting from scratch.

It's also worth noting that, even if this the version shipped in the initial batch of Lumia 550, 950 and 950 XLs:

• the new phones will continue to get OS updates on a periodic basis - and I'd bet on one within a month
• if you stay on the Insiders fast ring then you'll carry on getting new potential builds beyond 10586, ad infinitum. (If you want out, use the 'leave programme' function in the Windows Insider application, reboot and then uninstall this app.)

Plus just about every application and function is going to be updated on an almost daily basis through the existing Store mechanism. So there's plenty more to come.

Comments welcome. Which device did you try this on, which way did you end up going and how satisfied are you with the results?

Update: each of my devices so far (Lumia 830 and 930) has updated in-place without issue. Some reports from the Web indicate that Gabe's hard reset workaround, in the event of file corruption, isn't always successful - but I do wonder whether this is at all model or region-dependent. Ah well. Data points welcome!

PS. If you do end up with your phone in the boot loop:

1. Press and hold the Volume down and Power buttons at the same time until you feel a vibration (about 10–15 seconds).

2. When you feel the vibration, release the buttons, and then immediately press and hold the Volume down button until you see a large exclamation mark.

3. Once the exclamation mark appears, press the following four buttons in this order:Volume up, Volume down, Power, Volume down. 

4. Your phone should now reset and restart itself. (It might take a while for the reset to finish.)

5. As part of the startup sequence, choose your backup, if appropriate.