About a year ago I upgraded to windows 7,  I've had no issues of note, but I've not checked for, or updated windows at all.
 
Do you feel there's anything that has changed, that would be of benifit to my work with Sonar X3c and beyond?

If you haven't run windows update you should. Same with drivers and firmware. It should improve performance and stability, and if it doesn't that is what backups and rollbacks are for : It won't happen though.
 
Jury is out on windows 8.1, definitely update if you have a touchscreen but I really can't see much of an improvement otherwise.Oh the backup software is better as well.  I do use windows 8.1 but not with my DAW, one day I may adopt esp if drivers insist on it,  or I shall wait for windows 9. I like windows 8 but I'm indifferent to it, I don't see anything killer or "must have" about it. Performance may be a little better but it would be with no aero. Maybe turn off aero in windows 7 and pretend it is windows 8;)

I am not sure if I understand your question clearly so will hit all you mentioned quick...
 
Win7 - 64 - I will probably stick with this platform for as long as possible. No issues running with X3c. I personally have no interest whatsoever in Win8.
 
Windows updates - I would definitely recommend these, and turn on "auto updates." Stability issues and patches are addressed and usually available around the 15th of each month. These include vulnerability fixes (hacker response). You should have Win7 SP 1 (Service Pack 1) running on your machine?
 
X3c - Your signature mentions X2, so if the question was "Can I benefit from an upgrade to X3c on a Win7 platform?" the answer is yes. Stability is significantly improved, and the "goodies" included with X3 are significant.
 
Driver updates are also recommended - Iobit has a free driver updater (the official name is "Iobit Driver Booster") and it can be found at this link. This is a handy utility to update drivers in your system efficiently.
http://www.iobit.com/driver-booster.php