Paul,
Is the redistributable installing assemblies in the GAC? If so, isn't there a way for the app to just load assemblies that are "next" (in the same dir) as the executable?
I must admit that I personally don't like to force people to install "stuff" to run things. The thing same applies to Ageia's PhysX.
While DX and the .Net Frameworks are perceived as "general" installers, that people thing "well, these are really system updates", the Ageia drivers sound like "oh, no - more stuff perpetually taking up memory" and the GDK.Net runtime sounds like "oh, no - more stuff perpetually taking up space in system32".
While people will install whatever it takes to get a £40 game thy bought to work, a lot of people will not bother to litter their system just to check out something off the Net... at least if they are anything like me...
I have vague plans for World Domination