Isn't this problem due to gmail and not Mavericks - it doesn't work with Mail.app or web based gmail ?
Hard to say that it is a problem with Gmail when Google hasn't made any changes, Apple has.
Sending the new iWork documents as attachments does not work in Gmail via the native web-based interface or via the Mail app.
This does mean the problem is not inherent to the Mail app, but rather with iWork's new document format not being compatible with Gmail.
In my view that means that the initiative lies with Apple to improve compatibility issues its products have with Gmail, not the other way around.
In a business situation like my company is in, using Google Apps for Business, it means that we will be forced to revert back to MS Office if the issue is not resolved. We certainly won't change our email service for the whole company.
This new iWork file format compatibility problem is not limited to Gmail either. Dropbox cannot handle it either. It unpacks the content of the file in a folder as if it were a compressed archive.
The only way to share these files outside of iCloud (which just doesn't work in a business environment, and was never designed to) is to compress them in a zipped archive on Dropbox, and when you uncompress it, then the file is intact. However you then of course lose the ability to work with and update the document.
So something was not fully thought through on Apple's side when they created the new file formats for iWork. Either that or they are just are arrogant enough to believe that everyone will conform to their needs. The third alternative is that they simply don't care about it enough to ensure seamless use of their touted productivity software and have instead concentrated their resources on more aesthetic features like the web-based versions and iCloud collaboration, which, while a neat trick, do not have anything to do with real core productivity, especially in a business setting with the limitations iCloud has.