Google Apps Review
Ranked in these QuestionsQuestion Ranking
Pro Great integration into the whole suite of Google tools
Google Drive, Google Contacts, Google Docs etc etc. Using Google apps makes a lot of sense when you're already using a bunch of other Google tools. The organisation features (such as groups and permissions) turns the typically consumer focused products like Google Docs into fantastic enterprise tools.
Pro Uses Gmail for the mail client
Gmail is arguably the best mail client available, especially for a web app.