Those are bad examples.
you can take notes and go back and forth between notes and safari seamlessly - it will save the state of the app, so it will look exactly like it did when you closed it. You can IM while surfing with a push enabled IM client - I use beejive and safari at the same time all the time. You can listen to internet streams in safari, and it will stay open in back ground - I often listen to di.fm and bassdrive.com while reading twitter/IM'ing.
Now, my biggest issue is that I can't listen to online streams and surf the web at the same time, but everything else is covered by apple's "save state" mechanic pretty well.