Wow. Actually some folks I am ahead of in the list. I'm April 5.
For what it is worth I had build a little tool that predicts an approximate invite date based on the recent rate of invites and a given invite date. The last approximation was for the 21st of this month. It is obviously not accurate, but given how relatively consistent they've been in moving through the backlog, I'd say this is within a week of being accurate.
Bottom Line is that it is probably pretty safe to guess that we'll all receive our invites around the week of the 21st. Barring any major changes or an some factor like they got a surge of new waitlist requests around the end of March or Early April (which is actually pretty possible since that is when they started shipping).
Not sure if that increased or decreased your angst.