Yeah Sony puts the demo's on it's site with the latest firmware required that way it can coax people into upgrading.
Really what OS is your PSP? Also it's not a ta-082 is it? The newest downgraders for 2.01 -2.60 are very safe compared to the previous GTA required method. If your PSP is under warranty atleast risk it once and wait for devhook. You can always send it to Sony and have it upgraded under warranty.
Of course if you can't figure out how to create a folder named "update" in you psp's game directory and place your (unzipped) 2.80 upgrade eboot in it and simply go to your memory sticks game directory in the menu and execute it maybe you shouldn't try downgrading. Heck you should probably just avoid technology all together.
