Yeah, I consider my Plus membership to have been worth it as well. A ton of games, betas, discounts etc for a yearly rate equal to the cost of one new game. I have a PSP to take advantage of the ports and Minis that are given away as well, which probably makes a huge difference as opposed to someone who doesn't. A lot of the free games are PSOne ports or are from the "MiniS" section.
That said....I am skeptical/cynical/etc of a tier system. Its like the cable tv plans. That one thing I want most will be in one tier...and everything else will be in another. Sure, I can go cheap and live without that one thing, but if it is the most attractive thing about any of it...then why do it at all?
I am not sure that made sense. It makes sense in my currently caffeine deficient brain.