https://support.box.com/entries/20366301-Box-Sync-FAQ
Some select Limitations and Recommendations from the FAQ:
2 Limitations
2.1 File types blocked by Sync
The following file types are blocked by Sync:
Temporary files and folders (.tmp and files/folders starting with ~ character)
System and hidden files
Windows shortcuts
Box WebDocs
Outlook PST files
QuickBook files
Google Docs/Spreadsheets
Note: Hidden folders will be synced. Hidden files are not synced.
Versions Affected: All
2.2 Long file paths
Windows does not allow file paths longer than 256 characters. For this reason, Box Sync for Windows will not download any files that result in a path length of more than 256 characters. To prevent this, we recommend moving folders on Box to limit deep folder hierarchies.
The full path of Microsoft Office documents includes the drive letter, and all characters and folder names up to and including the name of the document. The entire path cannot be longer than 242 characters in Word, or 218 characters in Excel.
Versions Affected: All Windows
2.4 Mac bundles
Many files on the Mac are stored as "bundles", which is a folder that OS X is able to interpret as a file. This includes many iWork files, Mac Apps, NIBs, and more. Box Sync will not upload these files to your account.
Roadmap: We plan to support this in the future.
Versions Affected: All Mac
2.5 Links & aliases
Links and aliases are not officially supported by Sync. For example, Cross referencing links in Excel documents would be broken upon syncing to a different computer.
Versions Affected: All
2.6 Characters blocked by Sync
Sync does not support files or folders that contain any of the following characters:
\/*?":<>|
If you attempt to sync files or folders containing these characters, Box Sync will prompt you to rename the file or folder using the underscore character. In most cases, we recommend pushing the "Rename" button and accepting the renamed file or folder that Sync suggests.
Versions Affected: All Sync
2.9 Virtual Environments
We currently only support installing and syncing to the internal harddisk on the native operating system. Virtual machines and virtual user profiles are not currently supported.
2.9 Virtual Environments
We currently only support installing and syncing to the internal harddisk on the native operating system. Virtual machines and virtual user profiles are not currently supported.
3 Recommendations
3.1 Do not sync a large number of files and folders
Syncing a large number of files and folders can degrade your computer's performance. For this reason, we do not allow users to exceed the limits below:
Optimum Performance: 10,000 files & folders maximum
Technical Limit: 40,000 files & folders maximum
All previous versions: No more than 10,000 files & folders
Roadmap: We plan to increase these numbers for future versions.
Versions Affected: All
3.4 Do not install on Windows or Mac Servers
Although some users have reported successfully installing Sync on Windows and Mac Servers, this configuration is not officially supported by Box.
Versions Affected: All Windows