I had a similar scenario I needed to use the report viewer control in an asp.net app. The solution I came up with, was hiding the toolbar in the report viewer control, and creating my own drop-down selector for the various formats (PDF, Excel are the two we currently use).
The workaround is, when loading the report viewer control, I pass an additional paramter to my reports indicating "RenderType=HTML". When the request is made to get say the PDF Version, I use the same methodology, except I use the ServerReport.Render() function and pass "PDF as the RenderType Parameter, same for Excel.
This allows me to do conditional formatting/showing/hiding stuff in my reports for the various report formats.
Because the Report Viewer Webcontrol supports functionality for rendering specific pages/zooms from the code behind etc, it was pretty easy to build our own "toolbar" for manipulating the report, and gave us the advantage of styling it more suitable for our application, (although this can be done with css anyways). Another issue it solved was the weird print feature requiring the active x component, we implemented our own print mechanism to write the report out in a printer friendly manner.
Hope this helps.