Not sure what the focusing issue is that you're referring to but I find my X play focuses nicely. I don't have much experience before MM though, I bought it and two days later I got the update.
Multitasking is smooth, I have had a couple refreshes of webpages when switching back but maybe 1 out of 10 times switching back to Chrome.
As far as memory is concerned, it seems a lot better than my Moto G 2nd gen with Lollipop. I use to constantly lose my music playback. And I was using the light versions of everything. Now I am using Hangouts for SMS, have my Plantronics app running, music playing and other apps running (I don't use Facebook app though, still using Tinfoil).
It still seems very speedy and animations play properly. No stuttering when switching apps. Ill be honest, I was hesitant keeping the phone with how bad the stuttering was. Now I have no complaints.
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