See what others say about other email options, but yes, you can set BIS to get email from your personal email accounts (ISP webmail, yahoo, google . . . ). Yahoo, google, and windows live email is pushed to the blackberry virtually immediately. Others are polled at intervals of about 10-15 minutes.
BIS service will provide you also with internet access via the blackberry browser and any other blackberry branded data services, such as blackberry maps, pin messaging, etc.
By the way, welcome to the group!