To be honest I think that HTC's stance on SD cards has been their biggest hindrance. It has always seemed to me a big omission in their One series. Yes, I know lots of builtin is better but it's still a real tickbox. We'll see how they fare now they've embraced it.
Android users are almost by definition a fickle bunch where being able to switch easily to a different handset but keep the apps, etc. is important and a real hurdle for another OS. Nokia's X strategy is a not very convincing attempt to address this because it's focussed on the low end.