Have a look at the links below, which summarise the reasons to upgrade or not to upgrade:
Now here are some frequently asked questions about the Windows 10 upgrade:
Can I upgrade to Windows 10 myself?
We highly recommend every business should consult an IT company before upgrading to avoid unnecessary downtime.
How about reverting back to Windows 7 option?
What if Windows 10 is upgraded automatically?
Can we revert back and the repercussions of reverting back automatically?
Can we block Windows 10 upgrade?
Indication of time required to upgrade to Windows 10
How much time it takes to revert back?