Played this offline, wasn't great (bots were useless), but with a decent comunity I'd say this could be great fun. Some neat ideas and it looks quite nice.
I'd say it's worth the $20 (£13 or so) but it needs players playing. I coun't tell you how many servers etc there were but the fact it's rarely mentioned makes me think it's very small atm.
For those who don't know the aim is to kill another passenger on the ship, without being taken out yourself. Basically all the passengers are given a name of a passenger that they have to kill, so your hunting as well as being hunted. There are various weapons aboard that you have to find and use, some of the more obscure weapons (golf club, paddle etc) give you bonus money, otherwise you get money by taking your victims wallet. The money is used to buy drinks/food etc as you have to sleep, eat, drink, socialise whilst aboard but tbh this only occurs rarely so it doesn't disrupt the main aim of the game.
Also you musn't get spotted by either other passengers or video cameras (???) whilst attacking otherwise you get thrown in the brig.
It does look pretty nice on the source engine, but obviously not like HL2.