You made some very good points in your email to Simon. 

On Jan 9, 2008 10:22 AM, Emmanuel Lecharny <elecharny@gmail.com> wrote:

At some point in the future, we will try to avoid such situations, and
to release intermediate versions (like 1.5.2, etc) to include some bug
fixes. This is what we did with 1.5.1, a bug-fix release.

I know you meant we fixed a lot of bugs in 1.5.1 in addition to other things but I just want to be very clear to users that, 1.5.1 may have fixed bugs but it was an experimental release which also introduced potentially destabilizing new features.  I just want to make sure the words we use don't confuse our users into thinking 1.5.1 was a bug-fix on a GA release.  I don't want to aggravate users when they switch and see a bunch of API's have changed.

My primary concern here is in protecting our promise to users.  1.0.1, 1.0.2 ... 1.0.x are stablizing and (should) only be bug fix releases with no API changes.  1.5.1, 1.5.2 ... 1.5.X are potentially destabilizing and may break with the API and formats for storage etc.  Our promise to users is simple.  You should be guaranteed to be safe upgrading from 1.0.1 to 1.0.2 for example.  But don't expect this on experimental branches which are in the trunk.