Yup, I have the James Hobo in Deep Purple. The Deep Purple leather (also the same one as the Large Sasha at the Gilt sale) is a cowhide.
Hmm, I think you need to look at whether the Sasha at Gilt is a sufficiently good substitute for a lambskin Sasha or a black patent Sasha. It's definitely a really good deal, but if your preference for lambskin or black patent is really strong, then the black cowhide Sasha may not be a sufficiently good substitute. OTOH, if you think that the black cowhide is something that you could still love as well, it might be worth going for it!
BTW, I'm not 100% sure, but the Gilt description for the black Sasha states that it has patent trim (i.e. the vertical "belts" on the front and back of the bag, and the handles and shoulder strap). The pics don't seem to show it too clearly, but the trim parts
might be darker/shinier than the rest of the leather? If the trim is indeed patent, that might help!