What to see what a PSP game blown up to HD on the PS3 looks like? Well, you're going to have to work for it. In a recent Famitsu Ustream broadcast you'll find footage of this first of what will hopefully be many PSP-to-PS3 ports.
The problem is that the video stream is 45 or so minutes long. Andriasang says that you'll need to jump to about the 21:00 mark to find the game footage of Monster Hunter Portable 3rd HD. You'll have to put up with the voices of a bunch of Japanese onlookers yelling things like "waaah!" during the stream, but it looks great, so it's worth your trouble.