Office 365 is a packaged solution of 3 main features.
(Email, Calendar, Contacts) which sync to almost any device/computer and are kept in sync automatically
A way to collaborate on documents, contacts, versioning control, check in/out documents and easily make things like wiki’s, libraries, etc.
It’s hard to describe Sharepoint, as it can be almost anything, but it is most commonly used for businesses to collaborate and share things.
An instant messenger and online meeting area, like webex.
It costs about $12 a user and has a 25GB limit per mailbox.
The SharePoint site has a limit of 10GB
Lync has a max of 250 people
My company is currently hosted with www.appriver.com and they have had incredible service and really nice people, with a reasonable $13 a user, but it’s unlimited storage and we’ve never had down time.
There have been complaints on Office 365 and the service, also, there is no way to talk to them at this point. We are going to reavaluate the options in a few months.