Please share your GTD setup and experience: what works for you and what doesn't?

What software do you use and how?

I never owned a smartphone or a tablet, because I believed that they are mostly good for wasting time and effort on distractions (I have a Nokia 1202), but recently I gave in and bought an HTC One mini, because I believe it will help my productivity. Still getting used to the fact what goes for 'mini' these days, but that's the best phone I could find that looks well-made and not overly huge, short of the iPhone.

For my main computer I am running Ubuntu on a ThinkPad X series and I plan to upgrade to Microsoft Surface Pro 2; I think that it might finally be a tablet that I would use (because, if nothing else, it's a very portable PC). Yes, I want to buy a Microsoft hardware to wipe Windows and use with Linux, I believe it's that good.

So, I'm looking for your positive experience with GTD and related productivity software on Android, or maybe even native Linux platforms. I should be able to run Web-based, Java or even Windows apps via Wine, if really needed: in the best case scenario I just double-click exe-file and it works; I even used to play Hearthstone, when I had the time.

Do you find the use in a smartphone as a separate productivity device, even if you are near a computer?