I do straight line quilting and gentle curves with my walking foot. I also find it particularly helpful for doing stitch-in-the-ditch as it rides on top of the uneven seam sides better than my regular feet do. I have also used it when I am working on a very heavy or thick quilt (like a T-shirt quilt) to do every bit possible, even some curvy stuff, because it is so much easier to control the weight of a thick quilt under a grippy walking foot than it is under a slidy FMQ foot. My walking foot doesn't have the right configuration to do side-to-side stitches - I may have to look into that possibility!
You can do a lot of interesting quilting using just straight lines. I built up my machine quilting courage using a walking foot, and only started FMQing after I got comfy handling the quilt bulk etc under the (more forgiving) walking foot.
And welcome to the Board from North Carolina!
Alison