I don't quite agree with that.
- My Nexus devices have had really regular updates that have improved the experience. It's a Google experience, so it gives you the creepy crawlers, but it's a good general user experience, the best of ANY device on ANY platform for the moment. Several manufacturers insist on putting their own UI shell over AOSP, and where that used to be an added value back when AOSP really sucked in terms of UI features, since Android 4.3 Jelly Bean, AOSP offers the best UI experience over any Android UI, and several manufacturers have been downsizing their own UI (except HTC and Sony), so that updates to follow the releases of AOSP have been coming out faster and more often. However, users that have SIM-locked devices, have to get their OTA updates from their ISP, and those are notoriously bad at following updates, and are notoriously evil in terms of the integrity of the firmware and forced installation of spyware and malware.
- Samsung offers access to pretty much all the development stuff, and there is a lot of alternative software available. Samsung is the manufacturer that limits the hardware the least. They use MHL because it allows for turning the mobile device into a complete desktop replacement, instead of the functionally limiting Slimport which is preferred by the likes of Google that want to lock down the platform, they have SD card slots on pretty much all their devices, instead of locking down the internal storage like Google and Apple devices. And the Samsung hardware quality is still the best in the mobile business, with superior electrical engineering compared to any other brand. I agree that it might be an issue finding custom firmwares on English speaking websites, as there isn't much development in the US, but on an international level, pretty much anything is available. It's also not that hard to make your own firmware, it's just basic linux stuff actually, pretty much anyone could do it.
- On any ARM device, AOSP can be installed with hardware compatibility files for potential proprietary hardware that might be on the device, and it will work. Pretty much everything can be easily downloaded from github. There are some exceptions of hardware that requires proprietary things that are not really freely available, but most of those are gone now, or the code has been leaked or reverse engineered. Since Android uses the linux kernel, hardware compatibility is part of the kernel basically, and there isn't that much you can throw at the linux kernel that it doesn't recognize.
Only if it's x86
Not really decided on this one.
I like the concept of the unity between the tablet, PC and phone, particularly as I use a Surface Pro and Windows is my primary OS on my desktop PC but is it necessary on a phone? More importantly, on my phone?
I changed from iOS to Android before the release of the 5s not because I didn't like Apple or wanted to support Android or any other aspect to do with the manufacturer or operating systems, it was purely because Android devices are cheaper, they have cheaper contracts and (although I don't have it) they can be insured for less. To me, an Android phone still has pretty much all of the applications that I used on iOS but my wants for a phone (other than a mobile phone) are to browse the Internet and play a couple of pass-the-time games.
There were a few things that put me off of using Windows Phone 10's predecessors. One was the more substantial lack of applications. Sure, I don't use many but of the few that I use, if even they are not on the store that's pretty bad.
I had a couple of niggling issues with the older versions of Windows Phone as well. I'm not a huge fan of the tile system but it's ok. However, just having a list of applications when they're not tiles isn't very intuitive. The other niggling issue (which may make you laugh?) is the notification screen for text messages - when you just received one it's a wink, when you have had one recently it's a smile and if you haven't had one for a while it's a frown. I don't get a large amount of texts so I don't really want my phone to frown at me each time I look at the main screen.
Some of the interesting things that Windows Phone 10 is bringing to the game, however, is Cortana (which, purportedly, is also coming to iOS and Android. Way to steal the market!) and the proposed ease for programmers to be able to recompile their code from being written for Android or iOS to run on Windows.
The ability for programmers to recompile their code with that much more ease is a great idea but I can see that they might still be disinclined to actually bother if the popularity of Windows phones doesn't substantially increase. If they do get around to making it available for Win10 and there's a platform-specific bug but Windows phones are still not as popular then that bug will most likely be pushed down the list of priorities. I get that - it's business. However, for the consumer's point of view that's an annoyance.
Would I get a Windows 10 phone? Maybe. I'm more inclined to let Windows sit for a while on phones before I try it than a new version of Windows for a desktop PC.