It lets you have more lines of code and you can use local multiplayer and the mic and gyroscope and 3D and more sprites.

In short, it's everything Petit Computer was, multiplied by 100. Compare a DSI to a 3DS. It's everything, but much better. You have more lines for coding(original:10,000 this:1,000,000);performance is improved(SIGNIFICANTLY faster than the original); pallete system was replaced; You can have multiple programs open at once; This is just sctatching the surface! :)

they say it could have up to ps1 2d graphics

Overall, a lot more powerful, but there are also a bunch of tweaks to make things a lot easier. You can copy multiple lines of code now, multi-line IF statements (One of my personal favorites!), a reference guide which shows you how to use commands that you can have on screen while coding, folders to keep files sorted, and lots more! Definitely worth upgrading!

Awesome! I can't wait to get it then, so it can run more than one script at the same time?

Well, you have four different program slots that can be loaded at the same time, but I'm not sure they can all run at the same time. I haven't looked into that much yet.