The most common use of up lighting is in a recessed cove around the top perimeter of a room. To maximize light output use a T5 fluorescent or LED light source that will wash the ceiling with light. This helps to create a brighter ceiling that bounces and reflects light throughout the space without glare. Combine this with lots of natural daylight to increase the overall light levels in a room.
The light fixture should not be your only consideration — the type of lightbulb is equally important. Halogen compact fluorescent and LED bulbs come in a range of warm or cool hues. Much like the color of your walls the type of glow you want is mostly a personal decision. If your walls are covered in cooler tones you might want to warm them up with a lightbulb that casts a warm glow. Conversely you may want a cooler glow to brighten up a darker space.
Instead of or in addition to sconces hidden lights can add a general glow that bounces off the wall and into the room in an even subtler and more diffuse way. Cove lights are built into niches that hide the light source (often a plain LED strip) but hidden lights can also be obscured by medicine cabinets shelving or storage units.