I'm mostly working on software for ARM and since all the tools I need for work run well enough, why not? I still use x86 at home.

> which ARM machines have you been using as desktop replacements?

The ones I've used most were IMX53QSB, then ODROID-X2, ODROID-XU and I'm now switching to ODROID-XU3.

> What advantages do they have over x86 machines?

I was able to get rid of the x86 desktop while only using ARM hardware I would have used anyway. Also, the boards have a tiny footprint (you can tape several to the back of a monitor for example), they're very low power and can be passively cooled. They're very cheap too.

I've also used some RK3188-based mini PCs dongles for their portability. You can carry a reasonably fast GNU/Linux machine in your pocket and don't cost much more than Raspberry Pi, which I find way too slow.