My sewing machine

The machine I use for all my quilting is a Bernina Virtuosa 153, the old version with a clear plastic top on it. Mine happens to be blue, but I've seen other colors also, including red. This machine was later dubbed the Quilters Edition, and Alex Anderson's name was added to it. I formerly worked for a sewing machine dealer, and sold Berninas, so I had a very good idea about which machine I would prefer to have for myself. I had a chance to use them all, and knew I didn't want to do any machine embroidery (although that's a great feature to have for quilt labels), nor did I want the stitch regulator, which I felt blocked my vision while trying to free-motion quilt. I also felt that once I became comfortable with free-motion quilting that I didn't need the stitch regulator. The 153 was just the right fit for me, and had every feature I required, and none that I didn't. I have been thoroughly happy with it ever since I "adopted" it 3 1/2 years ago. I make sure to clean and oil it between projects, or whenever I see lint building up in the bobbin case area under the throat plate. This machine is currently not being made, but I have seen them for sale on the secondary market, so I highly recommend keeping an eye out for one. It came with a 1/4" foot, my favorite, of course, and a walking foot, which I consider essential for straight stitch quilting, attaching bindings, etc. Other features include a needle up/down option, a fantastic buttonhole foot (for garment-making), and the ability to drop the feed dogs. It also has a knee lift, with which I was already familiar when I started selling Berninas. I had worked in production sewing for many years, on a big industrial machine (1/2 horsepower motor), and those machines always feature a knee lift which is used to raise and lower the presser foot, almost like having a third hand. If you have a machine with a knee lift, be sure to learn to use it. And then use it!
Whichever machine you decide to purchase, be sure to do your homework first, and I always recommend buying from a dealer. If you buy from a store which isn't a dealership you won't have much recourse if things go wrong. A good sewing machine dealer will be able to service your machine, and should offer classes. These days there are so many features on most machines you might not be able to figure them all out on your own. Ask  your quilting friends about their machines, and see if they will be generous enough to let you try theirs out.
Of course, all this being said, you can make lovely quilts without a fancy machine. Our foremothers did it, and look at some of the masterpieces they turned out. It's just that many of the newer machines make things so much easier, and are real time-savers.
One more thing. No matter what some purists might say, it is not considered cheating to make quilts on a sewing machine rather than by hand. Ladies have been making quilts on sewing machines since the mid 19th century.