Great kit. Go for the III and definitely get the AA holder.
I'd get more than one back. The inserts are nice but it's nicer to be able to switch from B&W to Color without having to burn a roll. Get an extra darkslide if you can find one.
The Polaroid is great and easy to use. Last fall I took mine out and got some fun shots with it like this: http://www.flickr.com/photos/radstu/...in/photostream (that's two actually, scanned and stiched together for kicks)
The 50mm interferes with lens movements when your focus is set to infiniti, but it's still a fine lens. I own the 80mm and love using it. The 300 is good fun too.
I store all that in a storm case, it's easy to move around (relatively) and a great shooting experience.