Here are the version 2.51 (and version 2.50) patch notes:
Text fixes. Bug fixes. English voices added.
The following character has been added: Text fixes. Bug fixes. Battle version has been updated. Older replays will no longer be available.
More detailed patch notes are available via the official website.
The following downloadable content is also available today:
Additional Character Set (Eustace) ($6.99 / £5.79 / €6.99 / 800 yen)