John,
>I believe that you can attend sessions from all 3 regardless of which you sign up for. And a difference would be the conference materials. I don't think you get the CD-ROM and conference proceedings from the cons you are not signed up for.
According to the official website (which could be wrong or just marketing hype) you get the free pass to SQL by signing up for VFP by April 3. Conference binder and CD for SQL are available for $99 more -- I saw that during the registration process.
The last time I looked, you could *not* get a free pass to VFP if you sign up for one of the others. Maybe they'll just let everyone mix and match if they sign up for one -- sounds like the best idea to me, but I don't *know* what the real story is.