Should I update my Lumia 520 to Windows 10?
Although the latest build (10586.63) was released to the insiders, which I guess focused on basic fixes and stability improvement, there were no observable changes seen in 512 MB devices! (as I saw on many review channels)
Yes, although I am not use Lumia Phone, but if it is not the big update, I will not consider to upgrade.
Windows 10 Update for Lumia 640
My phone is the AT&T Go Phone version of the Lumia 640 I don't have my sim card in it yet because I wanted to play around with the OS for a bit ...