[brobinson]

I have no idea about usability because I don't use the online interface, but Microsoft's Office 365 offerings are great for $5/mo. You also get unlimited OneDrive space.

It also comes with 10 minute turnaround time on phone support. You get a little popup asking if everything is okay and if you want to receive a call for support when you login to the admin interface.

I've been quite happy with it for the last three months.