Pluses: nicely sized models can fit under any cabinets--purchase the right lengths for you kitchen. Excelent quality. Accent or task lighting with Hi, Low, Off switches on each light. Mostly invisible once installed with clean, even light.
Minuses: Installation not as easy as it might be. No fitting to connect from fixture to plug, so installation is for those comfortable with home wiring.
Tips: Large, channel-lock pliers (with tape over jaws to protect fixtures) work as an efficient way to squeeze open the electrical box (instructions say just squeeze with hands--nope!) 3 1/2 inches back from insde front of cabinet to screw hole works about right--more and the light is too near the wall; less and the glass will be hard to slide in and out. If using the (expensive) connectors to install, allow 2 1/2 inches between fixture and side of cabinet. Otherwise, plan on at least one inch.

My major concern was the level of light that would be available at the counter so I ordered the 30" 4-lamp model, with the thought that I could add an additional fixture if I wanted more illumination. I 'mocked-up' the fixture and plugged it in to see how well it lighted the counter, and it was perfect. So I proceeded to directwire it with romex to a circuit available behind the cabinet and installed the fixture in it's final location. I particularly like the thin profile, as it is hidden behind the front of the cabinet, and the high/low lighting levels.
The only difficulty I encountered was sliding the glass lens off the fixture. It fits snuggly.

I very much like the fact that these undercounter lights operate on a High or Low setting and are dimmable w/a good dimmeer switch.

I used this in conjunction with other sized light bars for my undercabinet lighting in my kitchen. I direct wired these and the installation (which I did my self) was fairly easy. The quality of this unit compared to some other brands seemed superior in materials and fit.
My only complaint is that the glass must slide forward to remove it for changing bulbs in the future. This forces you to mount the bar a few inches further back from the front edge of the cabinet. The other solution (which I did) was to mount the whole light bar just loose enough so you can slide the entire light bar to the side to have it come off of mounting screws. This will let me change the bulbs in the future and have the lights as far forward as possible.
I would recomend these.