From what I've heard from Lumia 650 users the AMOLED screen is quite nice, battery life shouldn't be too bad.
If you know what you're diving into on the software side I'd say you can go ahead, basically it's a 640 with AMOLED and more internal storage (though I still went with the 640 XL when I was deciding between 640, 640 XL and the 650 for the camera and size). 640/XL is still a nice phone though they run 8.1 better than they run 10.
I'm pretty happy with the app situation. It's growing in areas I care more about, all the stuff people do on tablets and PCs - all the fun stuff, bus stop games, music and art software, the browser etc. The social networks I use are all well covered. There's an app for my smartband.
It'll probably grow a little in the "phone app" direction too with windows on arm next year. Well maybe. At the least it won't hurt lol (given there will be tonnes of cheap windows tablets and hybrids with LTE, gps and calling).
And I'm keen to see how the Cortana skills api plays out on a phone with a Bluetooth earpiece (assuming mobile gets that, hence why I'm waiting till mid-may, and also why I asked about the speaker quality, should I decide to pretend my phone is a smarthome speaker)
That the screen is decent is a big tick for me. I'll be using my blackberry for business emails and poopy boring stuff, so part of the motive other than Cortana MS bots and alexa skills, and a general love of win 10 on other devices , is an actually useable screen for browsing on the go (when I don't have my tablet, hence why I don't need a big screen either, like a nice pocketable phone)
Basically this phone will be my driver. But I don't have a lot of technical demands from such a thing. Take okay pics, browse, open fb, play bus stop games, be a calculator, have a map.
BTW, can you currently use Cortana to make calls? (Seems this was introduced in CU on desktop, with no means to use it, but dunno if its on phone yet)
Sorry for all the questions, I'm kind of meticulous with purchasing research....,