I'm also interested in online/inline editing with Alfresco Share, and found this thread after googling for Alfresco/Zoho Integration.
I've seen Zoho integrated well in KnowledgeTree, but my clear DMS preference is Alfresco CE. All good point, Will, on examining Zoho's policies to ensure they are agreeable to what one wants to achieve. No point in editing a document inline if the owners of the editor's API/service own or have any rights on it.
For online document editing, I really do appreciate how Alfresco works; pretty much seamlessly with MS Office (especially on a Mac), and I use it constantly. There is occasional muddling about with temp/.tmp stuff, but this is a minor annoyance.
For inline (web-based) editing, I'm stuck. This is a huge feature for me since sometimes I prefer not to (or can't) work with locally installed editors. Sometimes I want nothing more to think about that the browser's cache rather than temp/.tmp artifacts.
If I remember correctly, Alfresco EE has Google Docs integration built in, but CE does not. Perhaps it can be configured in Alfresco CE 4.x?
So, in support of one of the OP's questions, does anyone know of a successful integration of an inline editor with Alfresco? The bigger question, of course, is "how do I achieve web-based editing of common office MIME (.doc/docx, .ppt/pptx, .xls/xlsx, OpenOffice/LibreOffice) types in Alfresco?
I'm really looking forwards to some interesting ideas or methods!
Cheers,
Trevor