I'd like to see a designer speak up about using stuff like this more than one time. I find I'd hard to believe that you would sit down, after already playing around with this once, and say "this time I'm going to add a chevron to each cell, put the button on the left side, and go test it in the hallway". If your app is a table with a stock navigation system do you really ever need to build a second version of the same thing?
Your website is cool, but If all you are doing is setting up some basic widgets like (tables and buttons) why don't you just use interface builder. It's way faster and cuts down on the use of these jerryatric noob tools. Who needs to show someone a prototype of a basic table view anyway? Moreover, creating stuff like this in graphics gives you the resulting assets and similarly creating in interface builder gives you the actual foundation for the app. What a horrible waste of time.