I would not ride without one. Had one on my 06 and now on my 09 Ultra. Absolutely a must have for any distance riding. I have the manual backrest. Once I have it where I want it I have found that I never adjust it again. Buy the way the manual one is adjustable also. Don't need no stinking lever on my back rest.
In my experience, the backrest is one of the best comfort investments (after a seat that fits). Add highway pegs and floorboard extensions and you will be smiling all day long.
I got mine from Chicago HD on line for my 08 SG. It's the adjustable one I wished it went back more, I have it all the way back . I think I am going to modifie the bracket so it will go back more. The other thing in some of the older ones they have a little pouch on the back to put sun glasses or what ever but the new ones don't .
Definitely get an adjustable drivers back rest. I got one for "longer trips" and haven't taken it off in over a year. An added benefit is it makes pushing the bike backwards a lot easier as you have something to push against instead of just pulling on the bars. And yes the HD adjustable will fit with the mid frame air deflectors, it is a little more interesting but it will work.
Anybody have an opinion on the drivers backrest? Do they make the ride much better? Can you actually kick back a little and cruise without being all upright and getting back pain?
Don't leave home without it. And get the adjustable one, it's worth the extra bucks.
I've bought a couple of Mustang seats and backrests from Ronnie and he is great to work with. He can get you just the seat or just the backrest or both as a package. Tell him Rick in FL told you to call and to hook you up.
I have a mustang solo seat with an adjustable backrest and I will say that it puts you in a more comfortable riding position BUT my SG vibrates so much that it transfers a buzz into the backrest which doesnt feel to good on the back after a while. So, I seldom use it.