I must be the only float guy on this board backreeling his spinning reel. I like this method for 2 reasons. First, if you put a slight amount of tension on your float when it's downstream from you, the hook swings downstream and is the first part of the jig to enter the fish's mouth. The float should not be straight up and down, it should be pointing slightly upstream. Remember, the speed of the current near the bottom is usually slower than on the surface. The speed of the float is easy to control(when you're upstream) by backreeling and adjusting rod angle.
Second, by back-reeling, I get a more solid and comfortable hookset than even the baitcasters do. If I miss a fish(rare), it's usually broken off. With 10 pound mono, I can reliably hook fish >120 feet away and I've yet to find my hookset limit with braided line (a 10.5 foot rod helps too). The one thing about backreeling, you have to have a certain amount of pull on the line from the current or from moving the rod-tip slowly upstream in order to avoid line spilling off the spool and getting tangled. I will open the bail if the current is slow and do as described by FFF above. Also, any line twist can make backreeling a nightmare. I keep fresh mono on my float rod or use braided line. I also use a swivel to attach my leader 1 foot above the jig. If I experience any line twist, I cut off the front 30 feet or so (more a problem with mono). Backreeling also works better if your mono is wet. The first 10 minutes of the day can be tough due to the dry line coiling and twisting really bad.
I fish the Clackamas a lot. It's a pretty big river. I think backreeling is more adventageous in big rivers.