In my opinion, ALL caches are worthy of someone... Some people are out for a challenge, and those people love the micros simply because they are harder to find in some areas than ammo cans... On the other hand, I FINALLY found a cache with an ammo can, and it was a tough find. But with my daughter along, I'd love to have her find a few, simply because it keeps her interested, and the micros are good for that. Not always obvious, but at least "findable" for a small child (she's 10, and not always easy to keep on track!)
I think a rating system, from experience with other "games" (4-wheeling multi-stop campaigns, etc) inevitably hurts the game, because the majority are looking for a challenge, and those who aren't, lose out because they can't find "just enough" of a challenge to keep them interested, while still allowing them access.
Hopefully this will keep on long after I'm gone, cause I'd like to be remembered as a cacher who kept after each and every cache, regardless of the community opinions of every cache. Some may be dumb hides, or lazy hides, but there's enough good ones to keep me smiling til the next weekend!