it seems that Google is purposedly limiting the idea of a GDrive even though you can upload any kind of files in Gogole Documents.

Given the cheap extra storage of standard Gmail account i have kind of given up my Google Apps account. However it seems that sync tools will only work with Google's partners and only with Google Apps premier...

Has anyone found a way to sync documents and files with Google Document like on Dropbox or Windows Live Sync

Sorry to bump this up but given how all geeks have been waiting for a GDrive for years, I find it very weird that no one ever developed an open source project to sync files with Google Docs...

Well I guess i'll stick to Dropbox

<< I find it very weird that no one ever developed an open source project to sync files with Google Docs >>

The API doesn't allow you to do that (unless you use Google Apps Premier), so it's not weird.

http://code.google.com/apis/documents/docs/3.0/developers_guide_protocol.html#UploadingArbitraryFileTypes

To clarify, the API does allow uploading supported data types (.doc, .xls etc.), see http://code.google.com/apis/documents/docs/3.0/developers_guide_protocol.html#UploadingDocs but only Google Apps Premier users can upload unsupported data types.

If you want to knock together, it's probably even possible to knock together a rudimentary system using GoogleCL (http://code.google.com/p/googlecl/) which allows commands such as:
   google docs upload the_bobs.csv ~/work/docs_to_share/*