The sync server is easy to use and very well documented. I have been able to set up syncs with both our office 365 (Sharepoint) and our local Exchange Server without any problems. There are some things that we would like to be able to do but there doesn't seem to be much support for them. We would love to be able to sync more than one folder at a time but this isn't possible.
We also would like to be able to add comments to documents as part of the sync process but this isn't supported either.
Pros
Easy setup
Great documentation including many videos.
Wide rangeof options available, even if it's just something simple suchas adding an additional field or changing how fields workin certain situations