I think StackExchange is great regardless of this feature (I am neither against it, nor in favour of it), but if you are going to implement it, at least consider fixing this bug.
On my smartphone (in my case an iPhone 5c, running iOS 8.3, latest as of June 6th 2015 - but I think this is related to screen size rather than specific device) the vote buttons are moving over the post when zoomed in. This is bad, because it makes both the vote count and - perhaps more importantly - the post itself hard to read.
Image of bug (top status bar cut off):
Edit: I forgot to include the solution I would propose: let the vote count go off-screen (i.e. only change y position (relative to the page, not the screen) and preserve the x position (also relative to the page).
If another solution is found preferable, I'm fine with that too. I proposed a solution only because I think it's better to say "I don't like X, maybe Y is a solution" than to just state "grrr I hate X".