I'm running Windows 10 Mobile on a Nokia Lumia 930 through the insider program and have build 10.0.10581.0 installed. It works like a charm and I would not change back!
This is better than every other phone I've have owned or have had access to.
I knew that they were slow with the updates, but this is just too much.
I have used the beta version of Win 10 on 640 and although I like it its still kind of clunks along the way and it did not carry over my copy of MS office so I recommend other do not upgrade till the full version comes along.
And What about Lumia 638 . I am a rather unfortunate owner of it ! It doesn't even have Denim ... still Cyan !! :(
Lumia 435 and 430 are newer like 532 and have 1 GB ram so these two MUST get Windows 10. So do all those having Microsoft logo on them since they are newer devices.