My 2 cents here.
Braid is great for spinning reels! Like others have said you get a really nice feel for the spoon or spinner, and better casting distance esp if you are chucking light metal. I run 20lb Suffix braid on my set up for coho/pinks etc. Good times on a light 9ft rod.
Braid is also good and necessary on the fraser for bottom bouncing, sturgeon fishing, ect. Are you going to spool up with 50lb mono. Yeah no. My fraser set up for bottom bounching has 50lb braid and I like it.
Braid for float fishing smaller rivers like the Vedder, IMO, is NOT a good idea. It is a rarity to see a "good rod" with braid on his level wind or center pin for this type of fishing. Why? First when float fishing, esp when the water clears up and especially for finicky coho, you are trying to keep everything as invisible as possible. Guys often use clear floats, small split shot, small swivels, light leader (often flourocarbon) and small hooks with small presentations/bait. Braid looks like cable to fish in clear water and IMO scares certain fish away under certain water conditions. Plus I find braid does not cast well when using light float fishing gear.
I remember last fall me and a couple buddies were float fishing a nice run for coho on the Vedder (water is low and clear). All using light mono mainline (12 or 15lb I forget), small floats and light leaders ect. We were doing quite well. Got into some chum as well and 1 spring. Guy comes along and askes for fish the same "honey hole." We say no probelm squeeze in. We keep hooking fish after fish. He is using similar set up (float, lead, swivel, small hook) but has braid on. He didnt hook a damn thing all afternoon! We told him it's your mainline dude, take it off and put on some good 12 or 15 mono. He said no way I'm just having bad luck or whatever. My buddy said, here, take my rod and fish with it. Guy was surprised but took it and my buddy fished with his. Guy starts hooking fish!! My buddy, who is a fantastic float fisher, hooked one lousy zombie chum in 30 min or so on the braid rod. Guy was sold and said he was going to spool up with mono before heading out next time.
Also it should be added that when tossing metal the fish often "zones in" on the spoon or whatever. Metal often really pisses fish off and they smash it and probably wont notice heavy leader or braid mainline. I often just tie braid right to my spoon or spinner if the water is murky. If it's clear I'll use a mono or flouro leader esp for coho.