Since your machine will not be the floor model, ask the dealer if they will be testing the machine BEFORE you bring it home. Also, ask the dealer if you can test sew on YOUR machine for a while before you leave the store. Plan on playing with it for at least an hour. ASK LOTS OF QUESTIONS! Keep asking questions until you are comfortable with your purchase.
The "tempermental" part of a machine just gets me. If I pay X amount of dollars for a machine, short of using postal twine, I should be able to run just about any thread to my liking!
But the old saying goes "Follow your gut feeling". If you really are not comfortable with the thought of your purchase then it really may not be a good fit for you.
Good luck!