Couple of Questions about RS2005

My client was using Reporting Services 2000, but is currently leaning toward
Crystal Reports XI. The reason being is that most of their data is filtered
through DLLs providing business logic. In RS2000, the only way to use the
DLLs as a data source was to write an extension and essentially hard code
the calls to methods and parameters inside the extenstion. Their complaint
was that every time they had to add something they had to recompile the
extension, send it to the server admins, wait for installation and so on.
With CRXI, all they had to do was point to the DLL as a data source and they
were prompted for the method to use as well as paramters and so on. Is
something like what CRXI (and CRX for that matter) provides in RS2005? Can
they use a DLL for a Datasource without writing a wrapper every time?
On a second question, another client of mine is using SQL RS2000 with
Oracle providing the data for the reports and VS 2003 as the application.
We are late in the developement of the application but are considering
upgrading to RS 2005. I have been unable to give them several reasons why
upgrading to RS 2005 would benefit them, since i can only see a few
drawbacks. One drawback is that they would have to use a seperate IDE to
create the reports (the VS2005 like IDE). One thing they liked was the
ability to run ad-hoc reports and use an embedded viewer instead of a web
browser (we currently have IE embedded in the app to display reports). I am
under the impression that the Report Viewer component will only work with
VS2005 (.NET 2.0). Is this correct? Is there any way to use the component
with VS 2003 and .NET 1.1? We can't upgrade the app to 2005 anytime real
soon. Also, a list of benefits to RS 2005 would be greatly appreciated.
Thanks,
Rob Edwards
For the first question, I don't see why you need to hard code the method calls. for the query language for their data extension, they can use a syntax like:

class.method (parameter1, parameter2)

They can parse the call, load their assembly, use reflection to grab the class definition and execute the method (look at Type.GetMethod) using the parameters. The extension never needs to change, just the business object.

For the second question, the ReportViewer controls don't work with VS 2003. You can, however, use VS 2003 to publish to RS 2005. You won't get any of the new report design features (multi-value parameters, end user sort, etc.) until you move to VS 2005.