We use the Math-U-See math curriculum, and up to this point, I have been satisfied with it. I am always tempted by catalogs and things that others are using, but this is one area in which I would like to remain consistent... at least until we begin pre-algebra and algebra.
Math U See is different in that it primarily focuses on one thing each year, and each week adds in review from previous years. For example, first graders learn addition and subtraction facts, second graders learn multiple digit addition and subtraction with regrouping, third graders learn multiplication, and fourth graders learn division.
The program very strongly suggests that students not move on until the lesson/ facts are mastered. I feel that this fits in with the classical M.O., because it stresses memorizing the facts. However, it is not only rote memorization... the students learn with manipulative blocks. The theme of Math U See is "build it, say it, write it," thus using several different learning styles.
The yearly kit comes with a student book, teacher manual, and DVD. This was the big appeal for me... I have a hard time communicating basic math concepts, and when I watch the DVDs with the kids, "Mr. Steve" gives me the catch phrases to use. The cost for a new year's worth of material is $55 (I think), and the workbook for a set of DVDs we already have is $20.
If you have any students older than sixth grade, I would love to hear about which math you use and why!