Of course, there are a couple of limitations to the deal. Obviously, you need to be a Verizon FiOS customer for this to work. Assuming you are a FiOS customer, and an iPad owner, you will be able to watch live TV on your tablet while you are on your home network. This will not replace your Slingbox, and won't work when you're away from home.
Lastly, not all channels will be available. Early reports have the number at around 75 channels (list is on Engadget.)
If you want to give it a try, just jump over to the iTunes App Store to grab the Verizon FiOS app.