I have the adjustable. I think it is much better than the old fixed.

 

I had a fixed backrest before and it was ok.
On my 08 I got adjustable. It is a lot better than fixed one. I like be able to make adjustment while riding. Also it helps when wife gets on bike.

 

I bought the adjustable HD backrest but it pushed me a bit forward than if I were riding without it. I put some spacers under the forward mounting point which tips it backward a bit and now I can use the adjuster to change my lean occasionally.