Yesterday i’ve installed WordPress 2.3 without too much problems. The new uptodate check for plugins is nice, out of question, but already yesterday i thought: hm, everybody is whining about Microsoft products phoning home, nobody gives a shit about wordpress doing the same.
The Nighwatchman has an in depth analysis about the data transferred to api.wordpress.org, read it here: Datenschutzproblem in WordPress 2.3 (Privacyproblem in WordPress 2.3).
I will use the following hack to omit my URL. Alternatively, uptodate checking can be completely disabled with this plugin.