I had a simple Jolly Jumper nursing pillow when I was breast-feeding my son, and for the most part, it did what I needed it to do. But it was sometimes awkward to get it into the right position, and as my son grew, I found that his body being supported at the same height as his head was kind of like you or I lying in bed on our side without a pillow...not comfortable and definitely not that conducive to breast-feeding. So I ended up hunched over and supporting his weight on my arm despite the pillow being there. It was not that great for my back, let me tell you.
When I was pregnant I heard a lot of good things about the My Brest Friend nursing pillow, and I must say, now that I'm using it, I definitely feel it is a good choice of nursing pillow, especially if you tend towards chubby babies that are heavy to hold in those long late night "feeding frenzies" (or am I the only one whose baby takes two hours to settle to sleep at night?)
It is made of foam and has a comfortable C shape that curves around the front of your body, and a narrow piece that goes behind your back. The narrow piece can be buckled to the front part (essentially so you are wearing it like a belt) or you can leave it undone. I prefer to leave it undone so that when my baby finally falls asleep, I don't risk waking her up by fiddling with buckles, etc on our way from rocking chair to crib. The top of the pillow is a uniform flat surface except for two small hill-shaped "pillows" which gently support baby's head while nursing. The cover has an attached pocket for any essentials, Vitamin D drops, or a book to read while nursing, or whatever else you can think of.
The cover is removable and washable, which is great, because few things see as much spit up as mommy's shoulders and nursing pillows... I'm not sure if the foam core is machine washable, so I always try to keep a spare blanket on the "business end" to help minimize the number of times the cover needs to be removed and cleaned.
If you are the type to need a nursing pillow, I would highly recommend the My Brest Friend pillow. You can find out more at http://www.mybrestfriend.com/