I use lots of precuts - especially for baby quilts and lap quilts, but I ONLY use Moda, because, as others here have said, the rest of them are not reliably 5"... never mind how pretty they are. There are a couple I wouldn't touch with a 40-foot pole. I think cheating quilters in this way will be the end of most precuts, because many people are understandably angry that their trust has been violated. The manufacturers have virtually shot themselves in the feet.
Now, to the second question: I love charm packs, layer cakes, and jelly rolls, but I do NOT like triangles at all. I'll make my own triangles, thank you. As for mini-charm packs and other half-breeds, I think they're way too costly.
Oh, one last comment: I never pay full price for them. Sooner or later someone will have a sale on what I want, or I find I suddenly don't "need" it anymore. <G>