ABC watches are great. Mine is Suunto X-Lander, and I love it. I find an accurate altimeter to be a very useful navigation tool in the hills at poor visibility, and the X-Lander barometric altimeter is just that. Plus, it allows me to get realistic ascent and descent values for my runs, unlike the grossly overestimated values one gets from a GPS.
There is also the compass. Electronic compasses have their quirks, in particular, they are very sensitive to tilt, so some ABC watches have a spirit bubble, and some of the newer models are tilt-compensated. The X-Lander is neither, but I found with little practice it can be used rather effectively. In fact I have got so used to it in the last few years that I rarely take a real compass with me any more. As it turns out, this past weekend I got a stark lesson in how a bad habbit that is, one I will not forget too quickly. »