These are all good suggestions. Another thing to consider is lessons. Will the store provide you with free one on one lessons? If so, how many? My store provides me with as many lessons as I want. There is a specific order she does the lessons in but she has moved away from that order when I have had something specific I wanted to discuss.
And the store I bought my serger from provided me with a free refresher course even 8 years after the initial purchase. I was impressed.