The stitch regulator was a big thing for me (I have an APQS Millenium on a 12' table), as was the automatic fabric advance. I don't have a computer and don't plan to get one.
One thing you might do in advance of attending the show is to go to the various Web sites of the machine manufacturers and look at the machines in your price range. See what is standard and what add-ons are available. Learn as much as you can about the machines, including pricing. The more information you know in advance, the less overwhelming it will all seem when you're at the show.