Update: MySQL 5.1 has been delayed until June. Source.
Earlier this year after much speculation, Sun Microsystems acquired MySQL for around $1 billion. And while there are still fears as to how MySQL will be affected by this purchase, for the moment things are running smoothly. To that end, the MySQL team has released a new version of the infamous open-source database, with the new v5.1 adding a host of features that should make it even more attractive to enterprises.
A VP for MySQL went so far as saying the new update brings enough substantial changes that they should be calling it 6.0 rather than 5.1 to highlight its importance. Regardless, improvements such as better reliability, and feature additions like partitioning, row-based replication and disk-based clustering can make it a worthy upgrade. From here on MySQL's development is under the watch of Sun, so we can expect it to become in one way or another a more serious competitor in the enterprise space currently dominated by the likes of Oracle and IBM.