My team has moved our project related task plans xls sheets to Zoho from current Goolge Doc's(Who is our official enterprise solutions partner:) ).

Why Zoho rocks?

1) Concurrent multi-user updates are buggy in Google Doc's
while Zoho fits in this space very well.

2) Zoho supports all major document formats & you can convert
your doc sheets to almost every major format supported by Industry.

3) Effective multi-user collaboration , friendly chat feature and
visually appealing than Google Doc's.

4) Zoho Meeting is the best
free online collaboration/web conferencing application available.
Google should work on this front to monetize their online collaboration
tool offerings.

Couple of suggestions to Zoho for improvement:

1) Missing Search feature in xls documents , ofcourse Firefox users
can use browser search feature but as usual IE sucks.

2) Zoho Meeting is indeed the best freeware available but lacking some
basic feature's:

a. Allow sharing a particular desktop application with other
participant user's instead of sharing entire desktop
(everything on your screen) because of privacy issues.

b. The Activex Control installation for allowing desktop sharing
is kind of buggy , many times resulted in the terminated
conference sessions & while the Java applet based sharing is
less responsive.

However,I am very happy to see a product suite from an Indian
start-up company overtaking Global technology mammoth.