Gel filters are absolutely the best. Period. I used them all the time before the prices went out of sight. Even then they were painful to buy.
Try using them in the field for a while in any other than calm, dry conditions. In Oregon, when shooting in the rain, mist, fog, or on the coast, glass just makes more sense, especially to the wallet. I switched to all glass about 5 or 6 years ago. No, you can't stack a bunch of them. I don't often stack filters, and if I do need to add a yellow to a polarizer, I just do it and move on. No one has ever looked at one of my prints and said "Oh, you must have stacked two glass filters on this one."
I have a filter wallet originally intended for gel filters. My nice B&W glass filters tended to slide out of it whenever I was shooting on rocks. I now screw them all together and put screw-on lens caps on the ends of the stacks. Bulky, maybe, but not that inconvenient.