My kids have grown SO much in math just in the last year we've used Math u See, and right now they are ready for a little break (double digit multiplication may need to wait a bit for my 2nd grader), so we're really enjoying RIGHT START MATH GAMES I bought in a kit. There's over 300 games to play ranging to all sorts of varying math levels. That way they are still reviewing and having lots of fun too. I'm sure we'll be back at Math U See as soon as we're ready.
Oh my goodness we've really loved the hilarious MATH series Life of Fred! So grateful my good friend told me about it! I personally don't see this at all as a comprehensive math curriculum but more as a fun supplemental to encourage them to learn math while ENJOYING it.
I've also heard great things about Teaching Textbooks, but I haven't tried it yet!