I have the KaysCase from Amazon. It works great for me to carry my Surface and to protect from bumps. I like the fact that it lets me have my touch cover. It is not perfect, but for what I saw, it is the best for my needs. Hopefully in time, they will have more cases to choose from.
UPDATE to my review of the WaterField Tablet Ultimate Sleeve Case from SFBags. (post #12) I ordered the recommended 43-27 size, and at first it felt a little tight. It has loosened up enough that it is a perfect fit now. And today I tried it with a Type cover, and the fit was snug, but I didn't need to force anything. It still slipped into the case easily.
I have been looking for a basic sleeve to protect my tablet when transporting to and from places and decided to try something different. I had my mother-in-law make me a basic one to try it. It actually turned out pretty nice (I didn't choose the fabric as this was a test run). I'm thinking of helping her pick out some fabric that matches the common colors of the keyboards (cyan, magenta, red, etc..) and maybe have a couple of different options. I only have the touch keyboard, but there should be enough room for the type keyboard also.
We did a velcro closure, but I think I could make it magnetic pretty easy. I'm also thinking about adding a pocket to the inside or outside for extra stuff such as headphones, etc..
This was pretty easy and cheap to make and the fit is great. It's nice can I can work on customizing it to meet my needs and fit the surface
So just to be honest and upfront, I have a total bag fetish, my wife accuses me of buying new technology just to buy a new bag, with that said the best bag that I've found for the Surface is the Targus Spruce Messenger for the iPad Targus Spruce EcoSmart I bought it at Target for $25 about 2 years ago but I'm seeing it inline for $40+. What I like about this bag is it is snug and has a very slim profile but I'm able to carry my Stylus, Pen, Smart Card and Reader, Power Supply, Tri-Fi Hotspot and VGA adapter. I've looked for a new bag but can't find one the does everything this one does, I did cut the fabric that held the divider so that Surface fit better.
I bought one like that and then returned it immediately. Having to mess with the Velcro that holds it in the case to open the stand didn't work very well and caused the tablet to want to fall out of the case.