Recommendations to others considering Sync Pro:
As with standard (not business version) Dropbox, this is a syncing system, so it doesn't work well if people need to be using the same files simultaneously, but we typically don't, so there's no problem for us there. Sync is an excellent solution if you're caught between the miserly 2 GB free of Dropbox and the 1 TB minimum paid. Review collected by and hosted on G2.com.
What problems is Sync Pro solving and how is that benefiting you?
When Barracuda shut down Copy.com, where our company had all of our files, we had to find a replacement. First we tried Google Drive because it offered 15 GB free, compared to 5 or less for everyone else, but it was quickly found to be a disaster. We did small tests with JottaCloud, but it seemed half-baked. Then we found Sync, and found it to be as good as Copy.com and Dropbox. (We used Dropbox before Copy, but its 2 GB free limit and high minimum of 1 TB for paid was not suitable.) Sync works just like them, such that all of our office staff (who are located in different states) can access all the files, and changes will sync quickly. Rarely is there a file conflict issue from simultaneous usage or because someone's computer didn't sync.
In addition to the Dropbox-style file syncing, Sync.com also offers a Storage Vault, where you can put files into storage so that they will not be susceptible to mistaken changes and syncing. This is easy to do -- to put them in or take them out.
Our company's files are about 10 GB, so we exceeded the free version. However, the paid tier we have is for 500 GB, which is for the combined space of the syncing and vault files, at only $49 a year, compared to most other services running at $10 per month (for 1 TB, their minimum) -- perhaps even $10 per month per user. That's another thing -- Sync confirmed that only one person has to pay for our files. I am the chief administrator, and I pay the $49; the others just access the shared folders as needed, and the storage they keep on their computers of my shared folders doesn't count against their free 5 GB.
We have been completely pleased with Sync. Review collected by and hosted on G2.com.