I can use the fmq bobbin case for regular sewing, but if I was starting a big project of piecing I'd pop it out and use the regular one.
You may need to fiddle a little with the tension before you start with the fmq bobbin case but once you have it make a note of it and you'll know what settings to use.
Also I don't know if I mentioned it or not but I have been freemotion stippling with my feed dogs up (happy accident) and the results are more even and less jumpy if you get what I mean. I still use the freemotion foot with the spring on it, but the results are more pleasing to my eye!
Patrice, the three things I bought were well worth the money! Please let us know if you find other items worth the expense for these beautiful machines!! What is top on your listÉ