If you also have Visual Studio 2010 SP1 on the machine there is a known bug that disables Intellisense in Management Studio. There's a Hotfix from Microsoft here:

http://support.microsoft.com/kb/2507770

Look...

According to MS you can update D-S-P unless you use merge replication:

http://technet.microsoft.com/en-us/library/ms143699.aspx

In our environment we had a 2005 Publisher with 2008 Distributor and 2008 Subscribers with no problem....

You do have to be careful about which servers you upgrade first:

http://technet.microsoft.com/en-us/library/ms143699.aspx

You can also abort a report (and therefore not send the email) by calling RAISERROR in one of your "Report DataSets". Your error text will appear in the SRSS log.

if...