We've used Horizons Math since K and really enjoy it. I have had the teachers guides for 1 or 2 years but never really cracked them open for anything other than checking the answers quicker. But I'm also not a scripted teacher. The TGs that are all laid out and basically say this then this now that irritate me personally. Horizons TGs are not as scripted as some, but it was still to much for me. I did look to it occasionally to see if the book had a different method of explaining something if dd was having trouble initially grasping a concept. I did take mental note of the drill suggested and the use or lack of manipulatives.
If there's a concept that my daughter knows cold that is on the days assignment *again* then I either allow her to skip it or do half depending on how well she knows the concept or the purpose behind the repeated practice.
She enjoys the color on the page and finds it easier to do multiple small sections of a concept rather than an entire page of one concept. If she needs additional review we simply find worksheets online, play at coolmath.com , multiplication.com , some other website or game, or make up some games or use real life practice (shopping for money & change, baking for fractions, etc).
The downside is it only goes to 6th grade. The upside is that after successfully completing the program through 6th grade the student will be able to go straight into Algebra without a need for pre algebra.