I am working on one now. The difficulty for me is that I read lots of books, looked at a lot etc...and I complicated it more than it needed to be.I didn't use a pattern, so it is all by trial and error for me. I wanted to do one where I didn't need to match seams, and somehow managed to be matching seams lol.I believe I only have 10 fabrics, those were hard enough to choose...I cant imagine 20! My advice is to find a pattern, and try to stay organized. It really is rewarding to see it come together, and it is worth it. Here is part of mine, haven't got much done since then.
http://www.quiltingboard.com/t-160704-1.htm