I'm pleased to report that we seem to be making good progress toward PostgreSQL 9.1beta. As we did for PostgreSQL 9.0, we are maintaining a list of open items that we need either to address or to decide that they aren't so important after all (there are also some issues that are being discussed on the mailing list that aren't reflected in that open items list). What we're really doing here is trying to stabilize the code, particularly with respect to the features committed at the very end of the development cycle. So far, the main problem areas appear to be (1) collation support, (2) changes to streaming replication, especially the new synchronous replication feature, and (3) the new serializable isolation level. But we are making rapid progress in sorting out the loose ends, and I feel a lot better about the release now than I did even a week ago.
Barring objections or unforeseen problems, I'm hoping to bundle an alpha5 release a week from today, on Monday, March 28. We haven't discussed the time line for beta yet, other than to hope that we'll be able to get there in April. I still think that's a realistic timeline, although there is quite a bit of work that must be done between now and then for us to hit it. In the meantime, if you're in a position to build from source, please keep testing and sending in bug reports. Thanks!