We love Life of Fred. I especially love that 1) they now have the series complete from start to college; 2) the lessons are mercifully short and the "testing" to move on is equally short and relevant; and 3) they're interesting stories that even my advanced reader (at 7yo he went through the Harry Potter series in roughly 4 hours/book) finds engaging. He is currently on the 5th book (which claims to be 2nd-4th grade level range) and is doing unions of sets (set notation starts very early), median average, subtraction with carrying, percentages and I forget what else. He's gone through the books relatively quickly partially because he really did already have a number of math concepts figured out. We started at the VERY beginning just to ensure there were no gaps. And it's an inexpensive curriculum.
I honestly thought we were going to need a manipulatives-based math program but this is really working well. I own Singapore 2a/b (where he placed in August, before we did any of the Fred books) but we've never used it. Although my son conceptually "got" addition, subtraction, multiplication and division, he didn't know his facts cold and that was apparently a critical factor before starting level 2. Ummm... then how did he place into that level?!?! (in fact, he almost placed OUT of that level). So we didn't start it this year pending learning his facts better (we used xtramath.org--a free program to help with math facts) and in the meantime, we started looking into and working on Life of Fred. He's learning so much in such a life-applicable way that I'm thinking to hold off on a more formal program until I'm looking at him potentially wanting to attend high school.
Life of Fred goes up through Algebra, Geometry & Trig for high school and Calculus, Stats and Linear Algebra at the college level. Someone on our homeschool e-mail list has a husband using the Fred books to get through his college Calc class. :) http://lifeoffredmath.com/