I have them, and like them. I have lower back problems occasionally as well, and these seem to help on short rides. For longer rides though I don't think they make much difference. I'm planning on putting on a backrest when I can afford it.
One thing I did find on my bike... when I turn the bars all the way to the left the riser juuuuust barely touches the speedo console, BUT that's because I have a tank bib on. It raises the console slightly.
