When I first heard about this, I just read it in passing. I did know that there was preview access to the service available and running. I have some experience with TFS. It was pretty good. There are some other good non-TFS ALM tools that are pretty good that I used while I worked at Medullan like Rally (http://www.rallydev.com).
Team Foundation Service looks pretty good, although, I have the feeling that it might require you to manage it from IE, but I’m not really sure about that at this point. You can check it out a series of videos on the topic starting here:
I particularly liked the following videos in the series:
I found this post from Martin Woodward to be very useful as well.