Hi Jana - hope you're enjoying your cruise! Can't wait to read your reviews, especially aftering seeing the pre-cruise cabin photos you posted!
Oceania@Sea charges for every minute you're online, whether or not you're actively downloading or uploading data. Note also that the internet speed via the satellite uplink is much slower than via land-based DSL or cable modem line, so it took me nearly twice as long to check e-mail or to download various webpages.
Despite the fact that we were unable to use the satellite link up for three days (there was no coverage over the eastern Baltic), I still managed to burn through 100 minutes just checking e-mails every other daily. I'd strongly recommend buying the 100 minute package for $80, as each additional minute over 100 will cost you only 80 cents, instead of the advertised 99 cent rate.
Something to consider is using your Oceania@Sea account if you need to compose messages online. You'll have your own Microsoft Outlook account, and you can take your own sweet time writing a message without worrying about per-minute charges. It's $2.00 to send or receive each message, so if you think it's going to take you more than 2 minutes to compose and send an e-mail using your personal account, you might as well save money and do it from your Oceania@Sea account.
One good thing about Oceania@Sea was that they allowed you to print unlimited documents for free, as Charles noted above. But as Charles may not have noticed, (or been too polite to mention) some staff took umbrage at the fact that we were printing off the sometimes-lenghty Yahoo Daily Digests at their expense, "abusing" our free printing privileges. Plus, I overhead them discussing how quickly they were burning through reams of paper, and what a problem it was going to be to order additional ones.
Regarding Internet Cafes, most cities seemed to have them - the only problem was finding them, particularly in places where the signs aren't printed in English. Another complication were those on-screen instruction boxes in the native language, telling you to do something in order to proceed. I didn't know whether to "Zlozyts Plzad" or to "Zlozyts Iszmir." Cultural experience is right!!! I didn't notice whether they were hooked up for wi-fi, however.