The N900's minor firmware update earlier this week (PR1.0.1) was to prepare for a larger update, and that larger update (PR1.1) is now being rolled out country-by-country. You can find the full technical details on the maemo.org wiki. There have been quite a number of bug fixes and feature improvements, including support for Microsoft Exchange 2003. The new firmware version should become available worldwide over the next couple of days, so if you can't see it yet try again tomorrow.
