We used Singapore only for Gr. 1for my dd. She HATED it! She had a horrible time trying to understand the way they were teaching her and came away from the year with the idea that she was stupid in math. We tried Right Start the next year, it was better, but hard for us to use and like you said, very teacher intensive. She did have some more understanding start to develop through this, though. Ultimately, the lessons took so long for us to get through (even doing only half at a time) that we were both kinda dreading each math time. I did not want her to feel that she hated math or have that type of mentality, so…now we do Math U See. We started her on Alpha in her gr. 3 year because we wanted to keep going over the beginning foundation and did not feel she had reached the point of mastery at all. We also wanted her to have her confidence built up in regards to math and conquer the mentality that she was not good in math. She did Beta this year and is able to do most lessons without much help. She understands better and feels better about her math now.
Anyway, I hope you get some other people write in about their experience with Singapore since my post was so negative towards it! LOL! I have actually heard that a lot of kids like using it and that it is a very good math program. In fact, that is why we got it to begin with! It just was not a good fit for the way my dd thinks, I guess. Sorry if that bummed you out at all. I would recommend M.U.S, though, wholeheartedly. It has really helped the entire math outlook in our home!
-Miranda