Upgraded from 10130 to 10158...
... on a cheapo HP Stream 7 tablet. It's not OK for a build so close to RTM.
An awful lot of bugs and annoyances have been sorted out. But these were my observations within half an hour of use:
* After upgrade none of the bundled Store apps worked, and even the Store itself wouldn't start. I ended up having to delete and recreate my user profile.
* An awful lot of dead files from the previous build were left hanging around, even after running Disk Cleanup.
* By default Windows now seems to think that the first day of the week in New Zealand is Sunday rather than Monday.
* It keeps trying to install English (United States) language resources, even though it's an English (United Kingdom) language installation running with English (New Zealand) region settings.
* I imported bookmarks from Chrome to Edge, and it worked OK, but managed to store them all in reverse alphabetical order with no obvious way of fixing them.
* In touch mode, you can still hear the gears grinding when an app is closed - it still doesn't always take you back to the start screen, and sometimes it does when it should take you back to a parent window / process.
Nothing showstopping in a 'suddenly bluescreen and ruin your day' way, but a mountain of nuisance bugs and fit and finish problems.
You also need to check and change privacy settings in half a dozen different places, Google-style, which is considerably worse than Windows 8.1. Some weren't respected and reset to 'send Microsoft everything' after the upgrade. All this is very concerning. And all that's before we get into the various UX deficiencies that have been discussed ad nauseam both here and elsewhere. Any chance of sanity prevailing now seems slim.
According to some reports, Microsoft will be preparing the RTM build any day now. Build 10158 must be very close to the final version that will be sprayed at millions of unsuspecting users and the mainstream press. It needs to be polished to a brilliant shine if Microsoft want to make a genuine effort to restore their reputation with regular users. (Not that I particularly care about Microsoft's reputation, of course.)
As it stands, it's not good enough.