I've been trying braided line lately and have found that 20lb braided works great on my lighter spinning rods for float fishing. I always use a leader that does fall at or below the rods rating though. And I've found you don't need to set the hook as hard when running braided - the line does not stretch, so a medium to light hook set will do just fine - just use sharp hooks... If a big fish runs, give them some freedom on the drag and point your rod tip in their direction. When they stop, tighten the drag a little (if you loosened it at all) and start cranking. With some experience, you'll know if your drag is set right by how it feels when you pull it off the reel by hand. Anyway, it can work, you just have to know what you're getting into.
Plus you can cast lighter baits\lures\floats\jigs better with the smaller diameter lines (or maybe it's just me...)