The Office 365 For Small Business and Enterprise plan is a great value for small businesses. Considering there are at least 3 million small businesses with 5 employees or less, Microsoft can expect to gain a ton of users. Training will be available at Office365training.com (not affiliated with Microsoft) for end users and plan administrators.
This article details the difference between the E and P plans. Many of the differences are important and hard to identify. For many small businesses, the P1 plan is a great fit. For others, you may want to choose the E plans - this document will help you make an informed decision about which is best for you.
Microsoft can and does update the services regularly, so while I’ve checked and re-checked the details, the services and capabilities do change.