[Huawei Mate 9 Questions & Answers] lostorbit:
This question is almost a month old now, but I'd like to put in my 2 cents in case someone else's wondering.

At the time of this writing, Mate 10 is supposed to be launched on the 16th of October and expected release is late October or November. If I was deciding between the two phones, I would wait a bit after the phone is available to see feedback on hits and misses, that's at the very least a month or two after release. So that effectively puts it at December / January for me. Other current factors for deciding between 10 and 9 is price as well how easy it is for you to resell should you decide to buy the Mate 9 now and upgrade later. I expect the Mate 10 to launch at a higher price than what you can get the Mate 9 for at the moment.

Huawei's marketing is promising big things for the Mate 10, even saying it'll be better than the upcoming iPhone, but I have a feeling that we've been through this before in the past and that we'll believe it when see it (not holding a breath here).

The rumours so far point towards improved, bezel-less display with slightly higher resolution, improved battery life and charging, as well as the possibility of seeing a new processor.

I would love too see a more globally available 128GB version (and to a lesser extent, a 256GB option). Speaking of internal storage limitations, it would be nice at the very least to have a dedicated SD card slot, making it easier to run a dual SIM setup without affecting storage capabilities. I'm not sure the Mate 10 would be addressing this. Waterproofing would be nice. I was a big fan of AMOLED in the past, but I think I may be leaning a little bit towards LCDs after using the Mate 9. Let's see what the 10's display is going to be like. I hope that Huawei doesn't go for a massive increase in resolution, in order to up their marketing game, as I'd hate to see it impact performance and battery life. I know all of you VR users would not like that, but the Mate is all about productivity and battery life for me. It would be nice if we can have higher, 4k resolution output to external displays though.

Now about the updates concern, I think it's a very valid question. And it does seem double-edged as some of the users have pointed out. I haven't had my Mate 9 for long (only a few days), but judging by what I read here, some firmware releases seem to have affected battery drain, although it's not clear to me whether this was caused by firmware approved by Huawei for mass-release or by users forcing installations of unapproved firmware.

On the other hand, security patches are important, and if downgrading was easy or straightforward, I would have said upgrade immediately and then roll-back afterwards if needed. Unfortunately, from what I can tell so far, it's not that straightforward. Nontheless, and regardless of how easy or difficult the process is, a good, validated backup is a must before any firmware upgrade or downgrade, and Huawei makes it relatively easy to backup using the built-in app which worked very well for me. I can very easily backup app data without the need for rooting (or enabling debugging), something that makes life very easy when upgrading and migrating.

To the user who said that it's messed up that a company would release a firmware that introduces bugs, I would say that the unfortunate truth is that many other companies are guilty of the same. Google is the first one that comes to mind, with long-standing and well documented issues on their Nexus line, particularly with battery drain and Bluetooth connectivity. So in my opinion, I wouldn't single out Huawei.

I do however feel that Huawei is, or at least was, very slow with major firmware upgrade releases, probably the slowest of all the major players. You can look up manufacturers track records for previous and current devices and draw your own conclusions (I get the impression that besides Google, HTC and Motorola lines are not so bad in contrast to Huawei, but that's just my uneducated impression). In the case of the Mate 9 though, looking at the firmware release history (check Team MT), I can see that the European (C432) and global Asian (C636) 'brands' are getting regular updates (almost monthly?). Although not all of those listed updates are necessarily approved for public release, it nevertheless does show evidence of active development. On the other hand, other regions such the US C567 and the Middle East C185, seem to get less frequent updates.

On the topic of major updates, we know it will get Android O. I have no idea whether it will get the next major update after it. My Mate 7 went through two major updates from Kit Kat to Marshmallow. of course, that doesn't necessarily mean that it'll be the same case with the Mate 9.

I wish major manufacturers would be more willing to release source code for drivers (and not just abide by the minimum source-code release requirement). It would definitely prolong the life of perfectly good hardware. If you take a look at Samsung, the situation is not that much better in terms of drivers' code release. Still, I would say custom firmware development on Huawei has got to be the worst among all the major vendors, with very little community backing. This could change seeing how some initiatives are picking up steam (see Openkirin work for other Huawei devices), but I would definitely not bank on it.

On the other hand, and as others have mentioned, the current firmware releases are solid and don't leave much to be desired, and I personally don't feel much of a need to root or mod the current state of this phone. I do run Nova launcher instead of EMUI, and phone seems to play nicely with it.

I was put off upgrading to the Mate 9 after the UFS 2.1 advertising scandal and waited as long as I could before deciding I can't live with the limitations of my previous device. Ended up going for a Mate 9 after all. Looking back, I wish I had gone for it much earlier as it's really a great phone and a pleasure to use.

Edit:

I forgot to mention that my device came with Toshiba UFS 2.0, not 2.1.