As somone already mentioned if you are trying to quilt free motion curves, cricles and what not, you need a darning foot, the walking foot won't do it.
The walking foot can do straight lines and easy small curves...but you have to stop and turn the quilt and not move it while the needle is going to get consistent stitches. Hoep this makes sense.
If you are just doing straight lines and you are getting uneven stitches, check to make sure that you walking foot is installed properly...there is an arm that needs to fit on a screw.
Hope this helps.