I think there's a thin line between a normal user's multi-tasking and plain out forcing the device to slow down.

Personally, I would use 4-5 browser tabs for facebook, gmail, maybe a flash webpage like youtube etc. On top of that, I might listen some mp3s, have an open pdf document, and also have a couple of ongoing IMs.

However, I would not listen to music while watching a streaming youtube video, nor would I launch a game just to see what happens to the device.

Desktop-like performance means multi-tasking reasonably considering that the processor is single core. It does not mean running every single application there is at the same time and expecting no slow down.