I empathise with you Jack. I have been managing a workgroup of 30, plus my personal network via Foldershare/Live Sync since it began.
Refusal to support XP is just another lever for Micro$oft to squeeze everyone to Win7. [after their pathetic flop - Vista, or Festa as it's referred to 'round here.]
Not gunna happen here !
Also note, MS never implemented the imminent improvements that Byte Taxi [aka Foldershare] had in the works. One of these was file locking, another, access control on individual sub-folders (group sharing aspects)
So I have recently been on the hunt for a replacement, just as you have [along with countless thousands, no doubt].
I don't want 'cloud' backup and remote desktops etc.
But unlike you, I do need group sharing with access control.
So ... for your investigation, here's my list:
Dropbox [.com] - simple, have been testing it for my stuff - seems OK
Sugarsync [.com] - complex, but supports groups, but limited security - testing it, syncs OK but sharing is problematic
Zotera [.org] - recommended by a peer - looks good, untested.
ZumoDrive [.com]
Syncplicity [.com]
GoodSync [.com]
That's atm.
Happy hunting Jack
Cheers Bob.