Welcome to the xbox subforums.

I recently had to connect to xboxlive through my sony vaio (windows 7) as I was living temporarily at my parents place. There will be some additional latency but ultimately it will depend on the quality of the signal from your router to your laptop. It was quite easy to set up by just sharing the connection. However, I faced 2 problems - Firstly my laptop kept going into suspend, so bear in mind that you will have to set your power options to always on if you don't want to keep getting disconnected, 2nd - It messed up my NAT settings to moderate, which means you'll have to mess around with port forwarding on either the router or your network controller. Testing your xboxlive connection through your console's dashboard is a good way of diagnosing if you have any problems.

Since you already have a mac, it doesn't hurt to try as all you need is an extra lan cable.