Bought from them many a time. Only games though and have always been spot on and good value for money. Would never pay for an OS though when they are so easy to get for free.
The game you can take with you from machine to machine, Windows 10 stays with the machine and is therefore a one-off.
Got my win 10 pro license from scdkey.com before cracks were reliable.
Paid the same £9.99 and its always worked fine.
To be honest tho if i had to put win 10 on now i would use a crack as they seem to work ok now.
I always install Win 7 first and crack that. Then I generate a GenuineTicket.xml. Then I install Win 10 and use the GenuineTicket.xml to activate it.
It's as though the original crack used has been "laundered" and the Win 10 installation is completely legal and crack free.