UPDATED 4/19/07
In some 'Better Late Than Never' news, Microsoft finally released Exchange 2007 Rollup 1 to the download site. When they originally announced this new servicing model, the Exchange team said Rollups would appear every 6 to 8 weeks. I have a feeling it will end up being quarterly... but that's just me. Anyway, Rollup 1 isn't published to Microsoft Update/WSUS yet... but I imagine that will occur sometime in the next 24 hours.
Exchange 2007 Rollup 1 isn't quite a Service Pack - meaning it doesn't include any new functionality*. However, the quality and amount of testing is far superior to traditional hotfixes. I wonder if this new servicing model will cause traditionally cautious organizations to deploy Exchange 2007 before SP1? Drop me a comment with your thoughts, and your feedback on Rollup 1.
* Note: Anyone been around long enough to remember the days when Service Packs didn't include new functionality? And what about the promise of a new SP every quarter? I digress ;)
4/19/07 Update: To reinforce the fact that Exchange 2007 is 64-bit only, Rollup 1 is 64-bit only. A 32-bit download was accidentally posted for a couple hours; however, that link has since been removed. And if if you have the 64-bit Rollup 1 and are thinking of trying it out on a 32-bit test system... don't. There's no hard-blocking in the code... so you can proceed through the install and break your 32-bit test system.