On 2011-07-24 I have entered some corrections: Grading of Curslacker Deich and other roads in Hamburg Vierlande, grading of a short road in Nettetal, interrupted road in Lorsch (Hessen).
Up to now they were neigther taken over into the main map, not even I’ve got a confirmation mail.
When you save your changes, they are stored in the the main database straight away.
Though it may be some time before a particular map rendering shows the changes. The default map on openstreetmap.org (Mapnik) usually updates within a few minutes or hours. But there has been some server problems over the last few days, which has caused updates to be delayed.
You can also try viewing a different map, go to openstreetmap.org and click on the blue “+” in the top-right, and choose “Osmarender”. It might be updated sooner.
Its also possible you are looking at a cached version of the map, you can try Shift+Refresh in your browser.