I've always felt like I had some deficiency when it came to viewing stacked area charts. I rarely liked them but couldn't put my finger on why (not that I really gave it much thought). This article's explanation of our eye's tendency to see thickness rather than the vertical distance is spot on. I find the stacked columns way easier to read, although if you had a lot of data points I agree with several of the other posters that a boring old line chart is going to be the easiest to read.