I bought a mummy style and then realized I dislike the inability to spread my legs. Also, the chest area is not large enough for my liking. The solution I've found is to open the bag and place it with the side seam up in the middle so the opening is facing down -- the bag is on it's side. This makes the bag function more like a blanket; this usage does require an extra, lightweight fleece blanket (or something similar) under the sleeping bag for warmth, but gives more room for movement.
Next sleeping bag I buy will be rectangular, or maybe instead I'll buy a good sized, lightweight down quilt.