I don't have much experience with the service but I will be getting it soon. As far as I know, coverage is about the same as post paid. Voice plans cost 5 dollars more than contract plans. This is a boon or a bane depending on ur state and what taxes ur state imposes. I know for FL, prepaid is cheaper since u only pay sales taxes on the service where as with post paid u pay sales tax, fcc taxes, regulatory fee, etc wich add another 10-15 dollars on bill.
Also data is still "unlimited" with prepaid smartphones versus the 2gb max with postpaid. The Droid 3 is priced at 394.99 currently which isn't bad. About $60 cheaper than the retail price and $200 more than the contract price.
I intend to get it prepaid since it will satisfy my need to avoid contracts and have something of a month-to-month service as well as unlimited data. Plus with it being a world phone I won't have to worry about contacting verizing to cancel or suspend when I leave the country for a bit.