I don't know if they've fixed the issue, but the Box client used to spike CPU at 100% on OS X. This would occur when you have a folder hierarchy with a lot of small files in it.
It turned out that their client was enumerating folders and files looking for changed data rather than hooking into the OS X file system notifications. We really liked it for the corporate account since it's possible to selectively grant outside parties access to files/folders.
It turned out that their client was enumerating folders and files looking for changed data rather than hooking into the OS X file system notifications. We really liked it for the corporate account since it's possible to selectively grant outside parties access to files/folders.