Downgrade to 1.50 -> Upgrade to Version 2.71 SE- B"
What is 2.71 SE-B" anyway? Well, it is the regular Sony 2.71 version albeit customized by someone called Dark_alex in a rather interesting way...it allows the 2.71 SE to run unsigned code just like the 1.50 :O
2.71 SE B'' also allows you to roll back to 1.50 if you don't like SE-B'' for any reason (even though there is hardly any)
This is the optimal solution as not only do you get all the features of 2.71 like web browser, RSS, themes etc.
And on top of that, you do not need any loaders or other homebrew to load ISOs, just dump a backup of your "ahem"(legally owned) ISO on the ISO folder on the memory stick, and it will appear in the games menu