I have noticed the same issue myself.

Last year we upgraded our reports from 2005 to 2008 R2. All went well and we breathed a sigh of relief. A few weeks ago I needed to amend some details and change a parameter - this was all done in Visual Studio and then deployed. It caused me a major headache when I kept testing the report and wondering why my changes had not worked.... I deployed again and same result - arrghhhhh... Luckily for me a colleague had recently had the same issue and had found the solution. It would never have occurred to me to go and make changes via report manager.

Simple when you know how but really frustrating to get ones head around it all. Why a re-deployment does not overwrite these details I still do not fully understand. :hehe: