My impression is that the books are all arranged in similar orders in terms of what basic knowledge and skills are introduced, but you can move at any pace that works for your kid. Each of my kids stayed on the basic method books for a very short period of time. I remember my DD8 (when she started piano at 5.5 yo) spent 2-3 months with a few method books that would usually take at least a year to cover, and then just moved on to standard repertoire. Even when she was using these method books the teacher supplemented with lots of other pieces as well. My feeling is that the books don't matter as much as the experience of the teacher who can tell what is the right content and pace for a kid.
In terms of books, I agree with aquinas that the RCM books are really good. But they are not method books, they are leveled repertoire books (meaning that they don't explain note names, time values, key signatures, expressions, etc). In terms of method books, aside from what has been mentioned above, we also liked very much Succeeding at the Piano by Helen Marlais.
