That's a good point, but I think BTS is soo much better for user adoption and that is more important, at least at this stage. BTS = Bitshares is obvious. XBS = Bitshares is not so obvious.
Also I think it should be Bitshares (Upper case B, Lower case s). The trend for lower case first letter for company names is just that, a trend. People used lower case first letter to differentiate themselves, but now that it has been done so much it is does not have the same powerful effect. Upper case first letter is the standard, proper, timeless way to name a company and will work. Also, we don't want to copy bitcoin's style, we want to differentiate from it for sure.
As for the lower case s, Bitshares flows, looks, and sounds better than BitShares.
PLEASE Make it Bitshares!!!