AST's vyo-pro protein bars taste pretty good for the little amount of fat and sugar they contain.
Chef Jay's tri-o-plex bars are decent, both in terms of taste and nutrition, but are extremely dry. Make sure to have a bottle of water handy when you eat one of these.
Muscletech's Nitro-tech bars taste good, but contain way too much sugar. The same goes for the Met-Rx Big 100 bars.
I only use protein bars when I know I'm going to be on the go or traveling all day, and eating my own prepared meals would be too much of a hassle.