I used the cheap under cabinet lights from Wal-Mart. I don't recommend that. They were way too bright and focused light on a small area. If you stood right by it, it would blind you, but walk a few inches away and you can't see your hand in front of your face...Jimmy
I used the cheap under counter lights from Lowes and they work pretty good...once past the switch issue. Left them in the not too bad looking metal case, but removed the transformer so that they would work on 12V DC. They are apparently "flood" lenses. The light is all directed down, but it is diffused. Installed a boat running light 12V switch so that either one or all three lights could be selected. Been pleased with them. The running light switch allows either one post switched hot or both posts switched hot. Keeps from feeding back.
Installing them in the box kept the lights assy pretty much out of sight, but no holes in the cabinets. A double panel on the over the sink cab would have solved this in a more workmanlike manner...but, hey...hindsight is 20/20.
The metal box is a good heat sink too...and the halogens get pretty warm.