We used Singapore for 3 years, but I was concerned that the boys didn't seem to be retaining the information and couldn't really use the information in 'real life'. I was also finding it harder and harder to explain.
We switched to RightStart at the beginning of this year. I have one boy in Level A (he's 5) and two boys in Level B (they're 9). I chose to put them back a year to make sure they had a solid foundation, which they lacked with Singapore.
Thus far we are loving RightStart. There was a slight learning curve at the beginning (mostly for me learning how to teach it). I had to look ahead and spend 10 to 15 minutes a night figuring out what I was teaching the next day. After 10 months I feel like I can sit down and just do it.
Things we like:
1. It's scripted so I feel like I can really explain how it works.
2. Lots of hands on games and activities. They remember the information longer because of the way it's presented. And there's less complaining!!!
3. Worksheets, but not too many. Most of the "drill" is playing games.
4. It's really helping them think mathematically.
Things we don't like:
1. Initial cost. After you have the manipulatives though it's fairly low cost.
2. Um, that's about it. We really do like it.
I recommend RightStart over and over to my friends. It's been a great fit for our family and I love to see their growing confidence in their math skills. As an added bonus, I feel like I'm learning math better than I ever know it before.