You can check out all of your applications to see if you're running any PowerPC software. System Profiler -> Applications -> sort by Kind. Only culprit on my system is some random CS4 stuff.
No it doesn't, I have it installed here and I don't have Rosetta. System requirements on the box says nothing about Rosetta and there's a big Universal binary icon on it as well.
If you didn't use Terminal to install Office, then you must have either upgraded Snow Leopard instead of doing a clean install, which would allow you to use Office without running the installer again, or you have Rosetta installed without realizing it.
Yes, I'm absolutely sure that I don't have Rosetta. It seems like an oversight on Microsofts part to require it for a universal binary, 3 years after PPC was continued.
Unfortunately, at least one installer (Microsoft Office 2008) requires PowerPC emulation. This can be worked around be installing the mpkg using the 'installer' command, but that is obviously not for the regular user.
Combine that with requiring CS5, and Lion will be a very expensive upgrade for many people.