NEW: Upgrade to 1.5.2

Read the dev blog.

Backing up your database and files is recommended before ANY upgrade

==== The official method.====
Upgrade just like any other upgrade:
– delete
/wp-admin
/wp-includes (but NOT your languages folder!!)
all wp-* files at root EXCEPT wp-config.php
(Leave /wp-content and /wp-images alone.)

– upload the replacements for what you have deleted (so don’t upload /wp-content or /wp-images)

Use the link in the Dev blog to read the Codex page on upgrading.

There is no need to run upgrade.php after doing this.

====The UNofficial method====
Right now I don’t have the changelog, but a list of the changed files is below. If you do it this way, you are on your own as far as support is concerned.
wp-admin/categories.php
wp-admin/edit-page-form.php
wp-admin/post.php
wp-admin/upload.php
wp-admin/users.php
wp-commentsrss2.php
wp-includes/comment-functions.php
wp-includes/functions-post.php
wp-includes/pluggable-functions.php
wp-includes/template-functions-category.php
wp-includes/version.php
wp-settings.php
xmlrpc.php

These can be downloaded from here:
https://firasd.ath.cx/wordpress-changed-final.zip

=====
Before posting questions, please read all other posts in this thread and also the Codex page. It may well save you time.