Before you install Service Pack 6, you should be aware of a few things.
1) They corrected something that has to do with Context operators.
Especially if you're filtering on a field that has Context operators in it, your filter isn't going to work anymore.
Example = [Hire Date] = Max([Hire Date]) in([Person ID]) used to be the way it worked prior to this ServicePack. Now, this needs to be corrected to:
= [Hire Date] = Max([Hire Date]in([Person ID])) in([Person ID])
The way that function works, actually should make it clear that it used to be bugged before -- but the result can be quite annoying -- the bug is corrected -- very good, but now some of your reports will not return correct data or return no data at all.
2) Variables can no longer have a name equal to one of the Data providers.
This might not seem a big thing, but it happens more than you'd think. One of the dataproviders is called employee.. and you accidently make a variable called employee. With SP6, this report won't even display anymore.
The solution we found is to open the report in an older version Rich Client, change the name of the dataprovider and publish the report.
But, Service Pack 6 does deliver some useful bugfixes. Java 1.7 works flawlessly and dates from excel no longer show up as 1/1/1970.