Which version of Debian x64 should I debug

[Bill Cox <waywardgeek@gmail.com>]

I'm trying to help build a stable version of Vinux x64.  I can still
read out of my right eye, and should be able to reasonably well for
another couple of years before losing my central vision.  My goal is
to help 64 bit versions of Vinux based on Debian and Ubuntu to be
fairly solid and feature rich by then.

Which 64-bit version of Debian should I be working on?  Lenny?  Sid?
Squeeze?  I figure this is probably the best list to post bugs on, as
I see more developers here than on the Ubuntu accessibility list.

Thanks,
Bill