Like Google Apps, Zoho provides solid collaboration from within the apps themselves. The collaboration tools are better here than in Microsoft's Office 365, but not quite as robust as what Google Apps has to offer.
Zoho allows real-time editing with multiple users simultaneously. In fact, it offers greater flexibility than either Google Apps or Office 365 by enabling sharing with any email address, and by allowing collaborators to sign in through a Zoho, Google, Facebook, or Yahoo account.
The Zoho interface is not as polished as the Google one, but the two are otherwise fairly close in usability.
Files and Storage
Zoho comes with a meager 1GB of online file storage. You can purchase an additional 5GB for $3 per user per month. The space allocated for Zoho email is separate from the data storage and is either 10GB or 15GB, depending on the service plan.
For email file attachments, Zoho limits you to 10MB, which could become an issue if you want to attach a document with lots of images, for example. You get no way to sync data for offline access, either, but you can use something like Box.net or Dropbox in lieu of a native option.
Zoho Docs has two pricing plans: $3 per user per month, and $5 per user per month. The plans are similar, but for $5 per user per month you can add twice as many workspaces, and you get a couple of additional features, including the ability to share documents with users outside of Zoho without requiring them to set up a Zoho account. In either case, email is a separate service that costs $2.50 or $3.50 per user per month depending on the Zoho Docs plan.
Zoho Docs is a capable suite of productivity tools. In many ways, it offers more innovative features than its competitors do, and it is more flexible. However, it doesn't stack up well against Office 365 in a Microsoft Office-centric world, and its pricing is not as competitive as that of rival online productivity platforms.