[al_borland]

At least a walled garden exists. Microsoft pulls the products that don't work in the market. So either you're left with nothing, or endless migrations as they keep trying different things without traction.

[cmxch]

If Windows Mobile* and maybe the Catapult FPGAs** are any indication, those are relatively lower walls than Apple.

The still unbroken(?) Zune and Windows RT are two rare exceptions.

* - from the HTC HD2 to the latter Lumias like the 1020 and 950/XL

** - buy a Quartus license and you have boatloads of small-ish DIY networkable Arria 10 GX accelerators at your disposal.