I see a big difference, but I'm doing things you said you don't need to do. Obviously, the apps made for the iPad 1 will always look as good as they ever did, and the type of apps you mentioned don't require a lot of horsepower, except for some games.
But my old iPad would crash with the iOS update and multiple-tasking, and crash after I would run memory/graphics intensive games like X-plane and big publications like WIRED and The Daily. I think there's just not enough ram in the first iPad.
Also, I DO want to run iPad 2 racing games on widescreen, 1080p on my big plasma display, so take my remarks with a grain of salt!