If you like cooperative games, I could recommend Guns of Icarus online. I've played it these last weeks on my brother's account and plan on purchasing it myself
What is it ?
In a nutshell, steampunk flying pirate ship to ship battle. Each ship has a crew of 4, with one captain who choses the ship + weapon layout. You have 3 classes to choose from, each of which can carry specific items to help them in their tasks.
The game is focused on crew teamwork and ship-to-ship combat, and hence there is no boarding (which is actually a good thing).
You have a lobby system, but waiting times aren't absurdly long.
GoIO isn't spec hungry, and it works well on Vista, despite the min requirement indication of Win7 (it's just that you're on your own if there's a bug, as Vista isn't supported).
So after some time here are some pros, mids and cons:
+VERY Teamwork orientated
+Good variety in weaponry
+Good work on the music/sounds
+No lag caused by sloppy coding
+++ More content is on the way : more ships, Adventure gamemode,....
~ All ships have a crew of 4, no more, no less, for now.
~ Campaign mode still in Kickstarter
-In game chat is not incredible imo; Mumble/Teamspeak/Ventrilo are much more practical if you are used to them.
-Skirmish maps seem huge, but are in fact rather small once you get to know them; I would have preferred bigger maps with more ships personnally. Only 1 4v4 map as of today. Others are 2v2 and 3v3.
A Lazy haiku
Cleaner is ubered
Bye bye sentry, 3 is cleared
Rifle fire. Headshot.
(Cleaner : Aww TEACHER YOU SHIT !)
Also, playing with lag is some skill on itself, lets see those bastards suffer