Just a quick heads-up on an issue we're starting to see more of these days. The reports in the Exchange 2007 Management Pack (MP) look great and work great most of the time but since they run using the raw data in the Data Warehouse (DW) they can time out and fail in larger sized environments. If you experience this you can always try to run the report using fewer servers and shorter time periods but in my experience this usually won't alleviate the problem.
So the bottom line is that if you're seeing these Exchange MP reports time out then hopefully this will save you some headaches running the SQL profiler and what not trying to figure out why they're failing. A better long term solution is being worked on as we speak and as soon as it becomes available I'll be sure to post about it here.
J.C. Hornbeck | Manageability Knowledge Engineer