1) Listed prices generally DO NOT include gratuities. Low level cruise employees like the cleaning crew, cabin stewards, waiters, cooks, etc. are paid ridiculously low wages, because cruise ships are registered to countries like Panama and the companies do not need to adhere to U.S. standards. I don't recall offhand, but for a 7-day cruise the "automatic" gratuity is, I believe, around $100 or so per person, so take that into consideration. You can remove the charge if you want to, but you'd have to be a pretty big asshole to do that :) Also, prices are based on double-occupancy, so if you go by yourself, double the fares.
2) Internet is expensive, slow, and charges by the minute). However, if you do this a lot, some cruise loyalty programs will give you free internet. I know Princess does this. Also, you're cell phone my work in certain locations. I'm a U.S. AT&T subscriber and I have full service in U.S. ports like San Juan and the U.S. Virgin Islands. If you can tether your phone, you'll get much faster and cheaper service that way than on the boat internet.
3) Don't get sick / injured. My wife stepped on broken glass while wearing open-toed shoes and got cut up pretty bad. The doctor on board used strips instead of stitches, and the cut reopened in two days, by which time we were already off the ship. The crew handled the incident terribly. The problem with the glass was not resolved quickly, my wife had to wait a fair amount of time for someone to show up with a wheelchair to take her to the doctor and the crew went into "don't get sued" mode really quickly. They gave us pushback when we refused to sign a liability waiver before getting treatment and we had some security guy who kept insisting to come into our room to photograph the shoes my wife was wearing at the time. When we complained the next day about the process, a nice woman sat down with us to hear out our complaint, but never really did anything. We were adamant about NOT paying for the care and it never showed up on our bill, so we let well enough alone. Three months later, they sent us a bill for $300 for the care. After we sent their HQ a letter in response, they ended up waiving the fee and giving us $100 credit towards our next cruise. Nice, but it was ridiculous in the first place since.
4) In regards to the above, had something worse happened, or they had refused to waive the fee, good luck fighting the cruise company in court. You're not only bound by typical consumer-crushing stuff like forced arbitration, but you're also getting into international legal difficulties. For big cases like the cruise that tipped over, it's worth the hassle, but for smaller claims, you're pretty limited in what you can realistically do.
All that said, I think this is a pretty cool idea and had always thought about how cruises could be a cool little work/vacation thing.