I bought from Cyntrix, and yes, this is official registered dell warranty if Cyntrix says so...
i called dell to check and have the 1yr warranty.

I updated to windows 10... no issues... and still CSGO, Skyrim, Dota2, and office and surf... like normal...
actually the startup is much faster... less than 10 secs into login screen...

I always update to the latest nvidia version...
my spec is i7, 4GB ram, and 850M.. with 1tb HDD (some sort of hybrid or something)..

I've updated for more than a month now... about 2 weeks after the launch...
i use it to watch movies... surf and play games daily...
never crashed, except CSGO one time, but after steam software update, not issue.

i update often since i left the windows to auto download...
i've heard that there may be some monitoring of my laptop and possible privacy breach...
but all my software are official and legal.. so no issues...

if you read some online articles about windows 10, they mentioned that Win10 will have auto update and apparently will scan your drive for pirated software...
not sure if this is implemented already, but i have no issues with this...

i am not a very detailed technical or a certified MS graduate, but from a layman uncle's POV by just using this to play some games, watch some movies and surf some websites... it is a good laptop and update to windows 10 is no issue.