My lessons (the expensive kind) 1. Buy the biggest hoop size right up front. If you get a 4x4 you will quickly want to upgrade. 2. Buy one that you can add the snap hoop to in the future (magnetic hooping is a dream!). 3. Make sure it has a USB port. Card readers are old technology and you shouldn't be paying for it in a new machine! 4. If you get a Janome or one that has restrictions on how you have to save the files to your USB drive (subfolders) make sure you understand it completely before you leave the store!
I've got the Brother PE770 (agree about the screen, but it's what I could afford at the time) the Baby Lock Unity which I absolutely love as a combo machine. and sew all the time with my sister who bought the Janome, and would love to trade for a baby lock.