It is a great site. I use it to get a general feel for a bike before I get serious about a purchase. It can show you basically how close your feet will come to flat footing, but it doesn't take in to consideration the suspension sag. Will show two up for different heights, too. . .
One big NoNo, I have forund is, do not hotlink an image of you on a bike, to show how you fit. The site owner will have it down in no time and post a big note in its place, "Don't hotlink from my site!". It may have something to do with bandwidth, or some other mysterious computer stuff. You can save the image as a jpeg for comparisons, but no url postings.