This is being written on July 21, 2016. On July 29, 2016, just over a week from now, Microsoft's free upgrade offer from Windows 7 or 8.1 to Windows 10 expires. Contrary to what you may have heard (or wished), it is not likely to be extended.
That means if you don't upgrade before July 29, you will have to pay for your copy of Windows 10. That could be decent chunk of change.
Unless Microsoft changes its pricing after the free upgrade period expires, expect to pay $120 for Windows 10 Home and $200 for Windows 10 Pro, which is the version every lawyer and law firm employee should be using.
This is not to suggest that you should upgrade from a well-functioning Windows 7 or 8.1 machine if you are not ready or if you have not confirmed that all of your mission-critical software and peripheral hardware is compatible with Windows 10. But if it is just fear of change (or laziness) that stops your from upgrading in time, it will cost you.