Great on Mac, less good on iOS
Overall Sync is great, and I have been very glad I switched from Dropbox. Just one big annoying problem. Accessing file structures from iOS devices is very slow. It can take minutes to bring up a list of sub-folders, and then minutes again to bring up the next level down. This part should be instantaneous. Once you locate a file, it actually downloads quite fast, but folder structures seem too difficult for Sync. This should be a big priority to fix.