Back on September 1st, I answered the question When will Windows Installer 4.5 be RTM-ed? with Q1 of 2008. Turns out that date was too optimistic. Q2 of 2008 now looks more realistic but, given the first optimistic mistake and in an abundance of caution to avoid compounding the first mistake, let's call just it Q2-ish.
For those of you wondering what happened, we've had a number of unexpected setbacks that required we either 1) cut features 2) reduce quality efforts, or 3) take more time. Taking more time is the best option available. We had believed until just recently that we could make the date but our best intentions did not hold up.
For those of you that also ship software for a living, the story of this slip may be familiar. Our chief mistakes were inadequately allocating time for a) unfilled positions, b) responding to user and partner feedback, and c) crossteam dependency execution. Through the cycle we saw these in small increments but it wasn't until the entry point for our Q1 glide path was missed that we realized the small increments were compounding.
As of the end of November, we're hard at working down our backlog of knowns. My reluctance to "set" a new date is because I'm not sure we've accounted for enough of the unknowns. 'Once bitten, twice shy' as the old saying goes. ;^)
We'll have another project status update before the end of Q1 2008.