I own one of the Casio models (its called a TripleSensor in my region), and has become a reliable part of my navigation system which is composed of:
- Casio PAG40B-2V for Baro/Alt/Temp./cardinal direction
- Garmin Geko GPS for Lat/Long checks
- laminated map with grease pencil
- Brunton 9020G (the lightest and most inexpensive compass with adjustible declination I can find)
I did not buy the Suuntos because they do not have a temperature sensor, which is important to me; but I see many more Suuntos than Casios.
I use the Casio to get me oriented in the right direction, the Brunton for sighting course/headings, the GPS for marking waypoints, and the map of course for reference.
I can not comment on the other posters bad experience, but the Casio sensor is accurate to .5', which is much finer resolution that you can read on the dial. In navigation terms, "drift" is not a characteristic of a compass, it is the tendency for a navigator to fly (or walk) to the left or right of course while maintaining a constant heading with, for example, an airplane (or body when walking). Heading is the direction you are pointing, course is a line along the ground. For example, an airplane might be pointing north, but a cross-wind from the East would cause it to 'drift' West. The airplane would end up far to the left of the intended destination and someone might blame the compass, when all along it was reading accurately.
Most people have inherent drift built in physiologically due to their stride (one leg longer than another, injury, etc..), and when blindfolded will walk slightly left or right of a straight line. Terrain and other features aggravate this tendency.
Interesting feature of the Casio, each instrument can be calibrated by the user very quickly. To align baro pressure with true altitude, correct the temperature, and even set the magnetic declination on the compass so it always points to True North at your location!
Casio has newer models which have all the features, but are the size of a normal watch. If I made the purchase again I would get one of those.