When I set up my first PJ, I fired the image onto a wall similar to yours. I had a builder in the house at the time and I asked him to help me put the screen up, ensuring it was level.
As we began the set up, he told me that he thought that I had wasted my money on the said screen as he thought that the wall looked great. However, during the hanging of the screen I lowered it and the picture leapt out even more, leading the builder to take back his comment
The colours were bolder, with more detail and better contrast.
However I would say that the screen definately highlights possible picture flaws, and I definately became more aware of the vertical banding on the first Sanyo Z1.
Its very subjective, but I prefer the screen.
Finally, I got my screen from
www.intoav.com
Its a 5' 8 electric grandview, also available in manual wind.
I hope that this helps.
Captain Benefit.