My 950XL runs buttery smooth after Fast Ring fresh install and I am very happy with it. However, with all the travel and banking I do, lack of apps gets frustrating. I used to have Android with Microsoft Band 2. I was almost completely paperless and cardless. Now, I'm back to printing boarding passes and a wallet full of cards.
If Surface Phone comes to market, I'll probably be on board. If not, I'm eyeballing the Nokia 8.
These are what I personally think are the four genuine reasons to not get a win10m phone. I don't really buy that uncertainty about the future of new features actually matters at all, to whether a phone is good, and does what its supposed to.
Uncertain future = pretty much bollox to me. All you need is a healthy app platform, and MSFT is so invested in that it basically HAS to try, even if win10m itself isn't doing grand, because its UWP, its the future of the whole platform. You don't actually need new features
However if you:
1) Bank a lot, in a way that depends on the apps
2) Travel a great deal, in a way that depends on the apps
3) Are very into IoT smart devices, that you don't want to have to choose specifically for the phone (there are watches, lights and devices etc but not as many)
or
4) Love the latest trends or are a teenager (I snapchat, pokemon go)
Any of those, you have a fairly valid reason for avoid the platform. I might also include other tiny niche user groups, like people that want 20 streaming services or similar.
All of those might change in the future, if windows on arm attracts ios devs to UWP, for laptop users, and that might bring more full desktop software too (at least IMO, the later). But right now its not a matter of "no apps" but distinct areas that are weak, and ones that are strong, such that particular kinds of users might have an issue, and other types of users (such as the basic every day user, or a photography fan, or mobile gaming, which are "solid enough"), not.