I like to see a variety of fabric patterns in a quilt. I think a plaid, check, stripe, etc. just add more charm when mixed in with florals and other fabrics. They're especially terrific in male oriented quilts, or homey type quilts. I try to add something along those lines to most of the quilts I make, when appropriate.
I do try to cut them straight, however - as that 'cattywompus' cut just drives me crazy...but I am learning to relax a little about that :)