I too say "Oh ess ex"... I was always under the impression it was "X"... I think saying "ex" is much cooler then 10, because "ex" is the part of extreme XD.
I used to Linux as "Lin Ux", but I have since found out that it is "Line Ux". I've also always up until recently said Ubuntu as "U Bunt To" as opposed to "(short)Ooh Bunt To".
That's how Linus pronounces it so I will too