I guess the best feature is document sharing, although I don't know with whom I would collaborate with enough gusto to warrant use of these web-based productivity applications. My serious collaboration happens inside the firewall, where Microsoft reigns supreme.
Therefore, I have no real use for Zoho, as I am covered inside the firewall and, outside the firewall, there are so many other ways to share information with friends: Facebook, Blogs, etc. However, it's nice to know about. One never knows what the future will hold!
BTW, I am writing this in and publishing this post from Google Docs because of my difficulties with Zoho. I suspect I would be more likely to use Google for this type of thing than Zoho anyway; it's just easier and, in my mind, a very trustworthy tool.