Then in the VSH menu (press select on the PSP home screen and go to the configuration) there should be a setting somewhere to "use version.txt", set it to true.
Only needed if you find something that refuses to run though.
6.20 Pro-B10 worked fine for me though I only tested it with a demo and PSX game.
Update and WARNING- You must log into the store and activate your PSP (through account managment) on the psp itself before you can use your PS3 to purchase/download stuff. If you try to activate it on the PS3 it will fail!