As David mentioned in his previous thread, we have been holding beta 3
on a handful of JS patches, chiefly "upvar"
(https://bugzilla.mozilla.org/show_bug.cgi?id=452498).  That patch is
getting close, but the continuing and great work on fixing other
final-release blockers means that we're accumulating a lot of changes
on the 1.9.1 stream that would benefit from wider feedback from our
beta testers.  To that end, we're going to wrap up beta 3 in the next
week regardless of upvar status; a 4th beta will follow approximately
6 weeks after, as a vehicle for more testing of tracemonkey, video,
places and other eagerly-awaited improvements as well as feedback from
beta 3.

(Contrary to some reports, this "upvar" patch is not being taken as a
performance win at this point, but primarily to improve correctness
and robustness.  It lays a foundation that we believe will give us
great performance opportunities in the future, which is wonderful, but
not what's motivating its priority at this point.)

Analysis of our crash stats and other feedback indicate that we're in
a good position with respect to stability and robustness, with key
areas easily identified and a good understanding of the work needed to
remedy remaining issues.  (If you're one of the developers churning
through those bugs every day, it's easy to be pessimistic about them,
of course, which is a trait I value in engineers. :) )

Please join the product delivery call today at 11 Pacific for more
discussion of this, and thanks to everyone for their great work on
FF3.1 so far -- it's shaping up to be a very worth successor to
Firefox 3!

Mike