Wanting more up to date feed back on people using these services now, the last posts I saw was when Cubby was a beta product. We have a client using VPN and SyncToy to sync about 40GB at present from several laptop users and a server. Each user only uses a sub set of the total data. SyncToy seems to have a day light saving issue (some clients overseas) where everything has to sync again after a change in either country. They have had flakey VPN etc problems and getting the staff to sync more regularly so seems a DropBox type setup would be better.
DropBox seems good but less flexible. Cubby also good but we had problems with one laptop where it just wouldn't work.
Won't mind paying something for the service, but probably want to go with something pretty well used.