For those of you who want to use MySQL 5.1 on etch, I prepared a backport from the experimental package of MySQL 5.1.22-rc. It's available for amd64 and i386, but will not be uploaded to the backports.org archive until there's a stable release in lenny.

Take a look at the list of Open Issues in MySQL 5.1 before upgrading your servers.

Mickael Marchand noticed a problem with the mysql-dfsg backport on amd64. I don't own such hardware, but fortunately Christian Hammers was able to reproduce that problem, which seems not to be Debian related, so he filed a bugreport to the MySQL bug tracking system.