I'm the opposite of you guys. I basically only use fluoro. I use Rio Fluoroflex Plus from 3x to 6x, and I love it. I never have problems with knots or splitshot. I used mono in the past and I still use it for the butt section of my leaders, but thats it. I can usually fish all day with 2-3 nymphs and a few splitshot, without changing tippet. I still catch as many fish in the first hour as I do in, say, the 4th hour using the same tippet. If the tippet breaks or gets scratched up, which is almost never, I change it. In December I was fishing a local stream with a size 22 para midge dry fly and small dropper about 3 feet down. I used 6x fluoro for my tippet and dropper and had no problem. It didn't sink the dry. That same day I was using a tippet ring, too. In fact, I've never had a dry fly sink because of my fluoro tippet. I'll agree that the cost of it sucks, but I go through way less tippet. I can make 2 or 3 nymph rigs at home and use them weeks later without any problems at all. I also like the fluoro because I'm clumsy and my tippet holder falls in the water a lot. With fluoro it can get wet and be fine, mono is usually ruined once it gets wet and dries. I've never noticed any issues with drag either, and I fish nymphs (Czech, Polish, French, American, Canadian, Bosnian, whatever they're called this week) most of the time. I don't see how similar diameter lines would vary that much, when it comes to drag. I understand that fluoro is more stiff, but with 2-3 weighted flies and splitshot, I highly doubt the stiffness comes in to play much.
I will state that not all fluor is equal. I've tried a few other brands and have yet to find anything that compares to Rio Fluoroflex Plus, not even the regular Rio Fluoroflex. I will use whatever equipment I have the most confidence in, and in this case fluoro wins, for me, hands down.