IMO, the first letter is usually typed right, unless it is switched with the 2nd letter like usperman.com. Ultimately, irishmat is right though...we can make all kinds of conjecture, but in the end, it's whatever traffic the name gets that gives it its value.
I haven't had much luck with typo domains. I registered gianrs.com and also businessweej.com. About 20 uniques a month for the first one and the second one seems to be on that same path.