We've used the K-2 levels before, or at least parts of them, & I just wasn't as impressed with them as I wanted to be. Not to mention that at the time they didn't fit the needs of my children. However, after much research the choice to move back to Saxon was really the one that best fit my needs, & honestly I'm quite glad we did.
The lessons can be rumoured to take quite a long time though, & that did concern me a little bit. However, as is the case with many things you adapt them to fit your needs. We don't actually do all the varying steps. Somedays we do the 100 Fact sheet, somedays we don't. I base it on needs or what I'm working on the most with the child at the time. I do some of the mental math problems to help encourage certain learners that they don't need paper to do math all the time.
One of the big things I do though is doing a considerable amount of the problems orally with the boys. I also won't have them do lots of problems of the same kind, I prefer to give them only a few of each kind unless they are struggling in a certain area.
All of this usually helps keep our lessons reasonably short averaging about 30 minutes or so, even with the hands on aspects of the lessons. I find that this really keeps things moving without boring anyone. So far we're really enjoying the change in the curriculum.