Best bet - use the internet cafe's at your ports of call. About $5.00 per hour is the going rate. Besides, they have much faster connections. The ships connect via a modem at about an average 47kps, which by todays standards is sloooooow and archaic.
Here's a bit of advice - from personal experience. Take along either a few floppies or one of the new little USB Flash Drives. Use the computers on the ship as a work station to type all your e-mails or work whatever files you need. As long as you are not logged on to the internet - there is no charge. Then when you get to a port - upload and/or downlaod all your e-mails, files, etc, via the floppy or flash drive.
It is quick and easy as I have done this on many cruises. Besides, it makes the time spent in an internet cafe the minimum. Gives you more time to be out and about and enjoying yourself.
Also, if you are a Crown & Anchor member, you and your spouse (cabinmate) should get coupons good for 15 minutes each using the ships internet service.