I installed HID lights in the wings of my Baron- they work great, use a lot
less current, and put out a lot more light. However, you do need some space
for the power supply, and the bulb itself is deeper than a standard
incandescent.

I wanted to put one on the nose gear taxi light, but because of space
concerns and the need to mount the power supply in the wheel well, where it
might interfere with gear retraction, stuck with the standard taxi light.

You will also need a field approval. We got ours approved prior to
installation, which then took around three hours a side. I got mine from
Xevision, since they make a 50W setup, which puts out more light, and was
also a bit cheaper.

Aviation Consumer had a great review of the various systems fairly recently.