So, I have already had one customer complaint about this or that not working on Vista.  That didn't take long.  So far I can see that:

-Vista does not ship with .net 1.1, only 2.0.  This wouldn't bother me as 2.0 is overwhelmingly backward compatible with 1.1 assemblies with very few breaking changes.  However my MSIs created with VS2003 demand 1.1.4blahblah explicitly, so I need to build new installers or include a 1.1 bootstrap.

-With 1.1 installed, my .net custom actions for registering my camera software with wia and doing some custom regsvr32 bombs and aborts the install.  Copying the files and assemblies needed and running the registration manually does not complain, however my 1.1 assembly will not start, giving an evil looking runtime error before a single line of .net is executed.  That's nice.

-My Camera software that uses the WIA automation layer seems to be able to register WIA events properly, at least I've got that going for me.

-Seemingly EVERYTHING requires me to confirm changes to my computer.  Manually Creating a folder under \program files requires two confirmations?  What the hell is that?  If that's security, I'll take my chances, thanks.

So, you can probably tell I didn't follow Vista very closely before launch, maybe some of these are known issues with simple solutions.  I'll be working on getting my company's most successful app installing and running under Vista now...