I think you can enable support for more products in the Google Apps management page. I have access to pretty much all Google products in my GApps account

No, it has to do with the single sign-on conversion. Docs is enabled:

http://dropbox.jedsmith.org/hn_1.png

But I get this when I click through:

http://dropbox.jedsmith.org/hn_2.png

It was a caveat I was informed of when I performed the conversion on my domain, but I didn't expect something flagship like Docs to not work.

> It was a caveat I was informed of when I performed the conversion on my domain

Can you explain that. I have no idea what it means.

Ehm, I have access to docs for all of my personal domains, and for my gmail account.

This is the menu that is shown that allows me to switch between accounts: http://i.imgur.com/tU5t4.png

You can still test it out by using the viewer to open files on the web, without having to log in; this can be pretty useful in its own right. Here's a bookmarklet that opens the link you click immediately afterwards in Docs Viewer:

    javascript:var link,l=0;while(link=document.links[l++]){if(link.href.toLowerCase().indexOf('.pdf')!=-1||link.href.toLowerCase().indexOf('.ppt')!=-1||link.href.toLowerCase().indexOf('.tiff')!=-1||link.href.toLowerCase().indexOf('.tif')!=-1||link.href.toLowerCase().indexOf('.pptx')||link.href.toLowerCase().indexOf('.xls')||link.href.toLowerCase().indexOf('.xlsx')||link.href.toLowerCase().indexOf('.pages')||link.href.toLowerCase().indexOf('.ai')||link.href.toLowerCase().indexOf('.psd')||link.href.toLowerCase().indexOf('.dxf')||link.href.toLowerCase().indexOf('.svg')||link.href.toLowerCase().indexOf('.eps')||link.href.toLowerCase().indexOf('.ps')||link.href.toLowerCase().indexOf('.ttf')||link.href.toLowerCase().indexOf('.xps')&&link.href.indexOf('javascript')==-1&&link.href.indexOf('file:')==-1){var newString='http://docs.google.com/viewer?url='+link.href;link.href=newString;}};void(null);

Does the Viewer work for you?

http://docs.google.com/viewer