We've got 5 devices should I upgrade to BES from BIS?

From BlackBerryFAQ

Why should my company upgrade to BES from BIS? - There are many reasons why BES is better than BIS

For End-users

• Full 2-way sync of emails including sent items
• Reconcilliation of mail items with the mail server - i.e. delete on the Blackberry and it deletes on the mail server
• Full sync of calendar, tasks, contacts etc
• Address List Lookup - you can just lookup a contact rather than having to sync them to the device
• Wireless backup of all information on the device (provided BES 4.1 or later)
• Access to behind the firewall applications - e.g. intranet and more

For IT People

• Very easy to trouble-shoot compared to BIS - no reliance on 3rd party mail services
• Control - devices can be 'wiped' remotely, clearing them back to their straight out of the box status
• Remote access to IT infrastructure - with BES you're behind the firewall..so being able to remote log onto servers enables IT admin from just the handheld