I bought a couple of Singapore books at some point to try with DD when she was in K, and found that we couldn't dip in and out of them without fully committing to the program. Also, it's totally personal preference, and I don't know if my kids would care, but I don't like the nonlinear, highly pictorial style of the pages. Just not my thing.
I think I have 1b and 2a. I just looked at these again the other day for DS, so they're fresh in my mind. I had heard so much about them and they didn't click for me. However, we didn't really try it per se.
