I'm having a nervous breakdown right now (my test is tomorrow at 12:30pm).
I'm currently taking my "8-minute-break" between quant and verbal.
Anyway, I'd like to shed some light on the Knewton practice test.
I signed up through the first link that BB posted; then in a couple of days, Josh emailed me with a link. The link doesn't seem to be any special link, but simply a link that leads you to Knewton's GMAT website. From there, I signed up for an account and took my practice test. I believe that's all you need to do (though I don't know if the same will qualify if Josh did not send an email out to each individual user). I took the exam and that was it...until tomorrow - D-DAY, baby.
One question to piggy-back on this thread, does anyone seem to know the correlation between Knewton's free GMAT test and the real one? Do we have a large enough of a sample pool to know the correlation?