I own both, and use both.
For me, it comes down to what you're doing and where you're doing it. I leave my type cover at home most days, and my touch comes with me to school and work. Thinner, more durable, and so much quieter - I can take notes and do research in class along with the course, without bothering classmates and/or interrupting class. This would be impossible with the type cover.
I use my type cover at home, or when it's not necessary to be quiet, or when I don't have a solid flat surface to work on. I can type almost as fast on the touch as I do on the type.
I am glad I have both keyboards, and I do recommend getting one. However, don't just buy a new one...the only reason I bought the other cover, was because I'm a smart shopper, and only paid $65.
Ebay is a great resource when you know how to use it - look for the right deals that are unpopular, and make the snipe! That's actually how I ended up with my Surface...I entered a reasonable bid with about 45 seconds left (thinking I would be outbid), and ended up winning the auction.