Microsoft is now selling Lumia phones with Windows 10 Mobile, but even Windows Central thinks it's not ready:
"I'm relatively savvy with this stuff. But I was ready to throw it out of a window before someone pointed out the non-obvious thing that I needed to do. This wasn't the only piece of out-of-box jank, either, to which I was told a new firmware update should 'fix' most of. It then took 48 hours for the firmware update to show up, download and install to the phone."
http://www.windowscentral.com/microsoft-lumia-550-review
It's a real shame. Windows Phone 7/8 was so great because it was like an Apple product done better than Apple: it didn't have "kitchen sink" features, but instead everything just worked and was holistically designed. In the original WP7 design, the borders between apps and the OS were faded to a degree that's unique. (This design was eventually lost as Windows Phone tried to catch up with app-oriented mobile rivals.)
In Windows 10 Mobile, everything has been rewritten as Universal Windows 10 apps that sort of look like the WP8 equivalents but work much worse (because they're really desktop apps squeezed onto a phone).
That kind of endless strategy-driven software rewrites are the plague of Microsoft today. The OP who is disillusioned with Windows Store mentions that the Store Dashboard got much worse when Windows 10 came around. Why? Who knows -- probably somebody at MS just decided that the Dashboard needs to be implemented using hot tech X rather than stale old tech Y.
This endless churn sucks and drives customers away. I quit using Windows Phone for good last year, mostly due to the customer-hostile Windows 10 plan and lack of new hardware. Can't say I've regretted it so far.