We've only just started using 1A, but I think it's going to work really well for us. It's mostly mastery based, which means we stick with it until he gets it. The spiral maths that we looked at made my head hurt just looking at the samples; they jumped all over the place. This is simple to explain, takes things step by step, and has just enough repetition to let us come back to it the next day if we need to. Both my son and I are easily overwhelmed, so having just one page to look at (vs a textbook then a workbook/notebook) keeps the focus on math instead of "what book are we looking at now". I also like that for the 1st grade level, once you get past adding and subtracting 0-10, you're encouraged to take the chapters in whatever order makes sense to you, or even add some spiral yourself and do 2 at once. I also like the price tag.
Grade levels used
No extra visuals, all-in-one book
Directions occasionally hard to explain to pre-reader
I wanted to like Math Mammoth. It has a lot of pros: It's economical, has no-nonsense explanations, there aren't extra books to deal with (all the teaching is contained in the worktext), it's mastery-based, and there is plenty of practice provided for each lesson. If you like the Singapore approach to teaching, MM is very similar, but easier to teach. Plus, you can go with the full curriculum, or you can use the topic workbooks to target areas your child is having trouble with.
I wanted to like it. My pocket book likes it. Unfortunately, my kids don't. It's one of those programs that I have tried repeatedly in different situations, but each time it is a fail. We used the full curriculum at one point, and we have also used some of the topic books.
What we had issues with:
The pages are cluttered and not aesthetically pleasing. Seems minor, right? Unfortunately, there is often not enough space for the child to write his/her answer or show his/her work---my children all prefer to use a worktext they can write in, so this was annoying for them.
While the author states that you can (and certainly should) have your child only do half of the problems unless she needs more practice, the sheer volume on the page causes a mental block for my kids. They need more white space. Spreading out the problems on the page and having "extra" pages that could be printed only if needed would solve that problem.
We also found that some of the explanations are problematic/confusing. This was true more with the higher levels (the young levels are much simpler). While I can teach directly in those cases, more than once I found myself having to look at the answers to understand what the author was getting at and in a couple of cases I found the pedagogy to be flawed. My husband, who has taught math to remedial college students and has tutored for the SATs agreed with me. I ended up teaching those lessons myself and ignoring the instructions given.
Math Mammoth has been revised since we used it---it is possible that some of the negatives have been fixed, but looking it the samples, it appears to still have the same clutter/too much to a page issue.
Grade levels used
All instruction is contained in the text (no tm or extras to deal with); economical
cluttered pages; sometimes explanations are unclear