So apple is officially at 6.81% marketshare. Not sure why this particular place is the end-all authority, but these are some interesting numbers….
http://marketshare.hitslink.com/report.aspx?qprid=10
PS: experimenting with a cut-and-past of an online table with some funky leopard/mail embedding thing going on… hopefully the table looks good on your end (i.e. the same as it does in the link)