Very nice technology. But I think you've chosen the wrong domain. I don't think there's a big (or even small) market in doing "pixel-perfect mockups". We have Photoshop for that, which (frankly) provides better tools than yours. I would take the technology (which looks great) and search for a better field to apply it to.
I found this quote while researching how to do something with Photoshop. Your post made me think of it. --- Question: Hey, how do I create a grey rectangle with a black line border, on Photoshop CS4? Answer: I would just create two layers, one black, one grey, and then use the select tool to select most of the black one (leaving a border) and then delete it http://www.thestudentroom.co.uk/showthread.php?t=839800 ---…
Create a rectangle object.
Step 1: Select the rectangle tool
Step 2: Draw the rectangle and edit color.
Step 3: Double click on the layer to open Edit Layer Style
Step 4: Select stroke and edit size, and color.
Done. I could do that in less than 20 seconds.