I finally got my Tinkerer kit assembled today (had it for months) and have been playing with trying to improve the FEZ Touch display response. I was surprised how slow it was when drawing eight 10x10 rectangles to represent LEDs to the screen so I started by trying to tweak FillRectangle. I was able to improve it a little and slightly improve the time to fill the who screen from 298ms to 257ms.
When displaying 8 individual 10x10 rectangles with FillRectangle it took about 520ms.
I then created a 10x10 image and added to the resources file. The time to display eight of the 10x10 images was 64ms!
When you look at all the buffer shuffling that has to take place for FillRectangle and compare it to DrawImage it is easy to see why using an image is much faster. The downside is that you are using more flash and the image size is fixed. Still for things like LEDs, Radio Buttons, etc it seems like it might be the way to go.