I have a tree of collections with thousands of files in Docs Premier, and I have a mirror which I update on my Win7 Ultimate x64 HP. I tried SyncDocs. It started out OK, populating the tree with new files, but after a short while it fell out of sync. That is, files were being poured into the main Docs folder and not into the trees. Then these flat files were synced onto my PC, etc., etc. It really made a mess of my Docs.
On another PC with just a couple of flat collections, SyncDocs worked fine.
There also is a terrible Google Docs bug (confirmed in a recent Case) that it cannot handle large numbers of files. In the main collection, you have to CNTL-RCLK and SHIFT-RCLK over groups of 200-300 files at most to get them into Trash. However, if you let Trash accumulate more than a few hundred/thousand files, you're screwed and you cannot Empty Trash. They keep promising they will fix this.