Yes, I have. As I remember, it's Android, correct? That could be a better option. I even considered the R6 but that's a lot more expensive. Maybe one day.
Reading through the responses, I'd like to point out that one VERY IMPORTANT factor for me is Fiio's great support. They listen to the community; they are easily reachable and even has live chat on their website; they are responsive via email; their authorized sellers worldwide seem to have that same customer-oriented culture and I like that. I have the A3; I have the K1; I had the X1 1st gen; I had the E12 and they never failed to answer my inquiries on time. Their website is easy-to-use and organized; where firmware updates can be easily downloaded per product; where you can easily view product features and available accessories; where news and updates are updated almost real-time. I cannot say the same, visiting other manufacturer's websites. It's easy to look past these if you're only considering price vs features but all their products have been designed for flexibility and convenience up to this point. And they always sounded great, at least to my ears.
Am I a fanboy? I'm a fan but not a fanboy that do not realize their mistakes. They seem to had a lot to address on the X1ii firmware. But bottom line is they addressed it, to the best of their abilities. And they listened, they always did. They'll always have margins for error and areas for improvement but they always listened.
Will I buy the R3 over the M7? Maybe. Maybe not. Depends on when I can audition them both side by side. I'm also thinking about just getting an A5 or Q5 because I love the convenience of my phone and it has a decent enough DAC (Wolfson WM8281). Let's face it, touchscreen is the way to go now, Android or not. We're not going back to the X Series type of navigation. Fiio is realizing that and trying to provide us something different, if not an evolution. Maybe they'd give us a direct competitor to the R3, if not this one, so let's see how they evolve yet once again.
Bottom line - customer support. That gets it done for me. Not buying from anyone else where I'll have headaches trying to even find a simple firmware update, etc. Hiby seems to have the same great support so we'll see.