I still find the polarizing filter to be the best solution to glare and color enrichment and NDs are still very useful in the field.

I find that split and reverse split ND filters are fantastic for landscapes and sunrises / sunsets. I also use polarizers for skies and fall foliage.

Polarizering filters will always be a necessity because the effect of cutting Through reflections cannot be recreated by software. ND filters are good if you don't want to take the time in taking multiple images and combining them later. These are the only two filters I carry. As for using UV or daylight filters to protect the lens, it not a bad idea, but when shooting directly into the sun, the more filters you have, the more likely you will have those pesky sun flares.

I use a UV for protection (and have had one give itself up for the lens) as well as a CP for both polarization and as an ND.

I use UV or Sky over all my lens for protection. I also use polarizing when I desire. I can view the results and if required I can reshoot for the desired results. I am more comfortable with this result, rather than using photo enhancing programs as the only means to modify the photo.

I like to see the results of using the filters while I still have a chance to reshoot if I don't like the effect I was striving for.