I got it in the last steam sale. It logs into Uplay every time before it starts. Maybe there is an offline setting, but I have no idea and it runs fine for me this way so I haven't looked for it. Great game. Even more to do than AC2. I am so enjoying bringing up my own group of assassin's and watching them get better.
how's the mouse working for you? I played it on a friends PC and it seemed the view would hiccup when I moved the mouse to look around, like they didn't implement mouse smoothing properly.