PSP Go is more for the digital fan. Which is what Sony has been stressing. It won't replace the 3000 series or UMD. It's to target the people who don't like the size or UMD. Which there are alot of those people around. I find it interesting that I would read comments from here, joystiq, GiantBomb, Gamespot and IGN about how useless the UMD format is. How it hampers the portable status of the handheld. So Sony makes the PSP Go. Which is all digital (but they still have the 3000 series), smaller and the battery will no doubt last hours longer. If you don't like the product. Don't buy it. Simple enough. You won't change the minds of the already going to buy the system.
(This post isn't meant to change anyone's view of the PSP Go, but I want to make sure people understand what this system is)