I use a Sekonic 508.
Lack of sensitivity: At first I thought its lack of sensitivity (not getting a reading when the light is really low) was a drawback, until I found by experience that metering when it's that dark is pointless as the film recipricosity corrections get huge and the light changes a couple stops during those long twighlight exposures. Turns out low-light photography is more art than science. Use the existing-light exposure charts.
Existing light metering: Very nice when I can't find some spot to meter. Typically I can find some zone 5 rock or clump of grass, or some bright zone 6 foliage to meter (I shoot transparencies, by the way, not B&W). But if I can't find something in the scene with a brightness level I trust, I extend the dome and get the incident light reading. It's usually a good exposure, but I often feel a lack of certainty in how the bright objects will appear. However, a spot meter can do exactly the same thing if you have a gray card or a 'calibrated' object you can meter instead (the palm or the back of your hand, for example).
Flash metering: A very nice feature when I do portraits (rarely). It will combine multiple flashes (from different lamps) for an overall exposure. It also indicates relative exposure from each flash.
Reading in viewfinder: This is the one thing I really miss. I'd like to see the EV reading inside the viewfinder of the spotmeter as I move from object to object. This would make it much easier to assess a scene for latitude (the brightness difference between the brightest and the darkest visible objects). For now I can point, click the meter trigger, look at the EV number, and repeat until I have the range. Some use of my own memory required.
There is, however, a memory button you can press to 'save' three readings and have them displayed on the analog exposure scale. I can then turn the wheel on the side (to select the shutter speed or aperture) to see where the three memorized exposures end up. This was a handy feature while I was learning exposure, but I don't need it much anymore.
Incident v. spot: I find in general that the spot meter is far more useful a tool than the incident meter. The sort of decisions I make in the field: how bright do I want that rock to look? or what features in the scene am I willing to let drop into the shadows? are best answered with individual exposure readings. An indicent-light meter would get the overall scene exposed at the zone 5 level, but that leaves the exposure of the interesting things in the shot a little more to chance than I like.
Analog v. digital: I could use an analog meter just as easily as my digital meter. My digital meter automatically lights up when it gets dark, but it's not that big a deal: I go to the charts when it's too dark to read the display unlit.
Lenscaps and watertightness: Very important! My Sekonic meter is beat up bad, all scratched, permanently dusty on the outside, but becaus eit has a good lenscap with a lanyard, the front lens if still pristine, so I don't worry about lens flare or side-lit dust increasing my exposure reading. I shoot int he desert mostly, so I haven't needed a watertight meter, but the water seals also keep dust out of the meter, including the battery compartment. Not that a dust-free battery is important, but I know that when the battery gets dusty, it's time to worry about dust on the sensor.