Congrats on your purchase. I recently "went over to the dark side" myself. I switched from a Galaxy Note 4 to an iPhone 6s. I bought an iPad mini 4, and an Apple Watch. (I still use both my Surface Pro 3 and Surface 3. I also still use my Microsoft Band, although it's not playing nice with...
I'm not judging it. In fact, I have it on my SP3, and love it so far. ::knocks on wood:: I'm just worried about it slowing down the slower processor of the S3. Lagging really irks me, and Win8.1 runs so smooth on it now.
I finally installed Win10 on my SP3, but that's a more powerful machine. So far, it's working well. Not sure about battery life yet.
I'm leaning towards keeping Win10 off my Surface 3 because I think it would slow it down. That's why I wanted opinions. :)