The first patch for the retail version of Unreal Tournament 2003 is in beta stage according to Epic's Steven Polge, who released details of issues addressed and gameplay tweaks incorporated in the update on an official mailing list. This list has since filtered through to the official Infogrames forum, and you can read it here.
Gameplay tweaks and fixes number the most, with changes ranging from the obvious (suicides now count against team score in team deathmatch) to the obscure (minigun spin-up time is reduced slightly). Other fixes include a CD check problem which affects some machines and support for Windows 98 from the UnrealEd editor supplied with the game.
Epic has yet to release the patch or confirm when it's due out, but expect to see it soon.