Ranked in these QuestionsQuestion Ranking
Pro Full-featured collaboration solution
If you are looking for an alternative to Gmail, look no further than Zimbra. While not a complete document solution it does have some document features as well.
Con Heavy and monolithic
Zimbra doesn't much work with its host platform as much as it brings its own copies of utilities. If you want something small and "plays well with others" integratable...this is not it. Too heavy to run on a RaspberryPi if you're looking for something for just a few users.