Well I'm not sure if it was the changes I made, the requests from Roms Rants or the sheer luck of being in the right place at the right time and getting linked from MSDN but as of last week The ZBuffer finally shows up in page 2 of google for Managed DirectX and on the first page for "Managed DirectX".

• MSN Search has me in 2nd place right behind Microsoft (I can accept that)
• Yahoo list me 4th but again behind 3 Microsoft links
• Ask Jeeves is a little less generous, insisting I'm a page 2 kind of site

So there's still a little work to do to convince google. Rom's Rants suggested that including the words Managed DirectX inside the link rather than just The ZBuffer may help.