I have owned the 24 on 2 different camera systems and when it came out it was the best option for shooting that wide without stitching. The issue with it, as others have mentioned, is that it needs a 2 stop center filter to make it useful, so a 1 second exposure become 4 seconds, and 30 seconds becomes 2 minutes. It has very limited movement for sure and does suffer from less sharpness at the edges, but is super sharp in the middle. It also is a symmetrical design and has very little distortion.
The 23HR weighs a ton more and is much bigger due to its retro-focal design (which means distortion, but is correctable with the Alpa Lens Corrector software). This lens gives much more movement, does not need a center filter, and is very sharp edge to edge. There's no comparison really if you have the funds. I rarely even adjust the focus since its so wide, one setting works for 95% of the work I do with it, so that just contributes to the speed of working with it.
All of my other lenses are Schneider which I like very much, so this is my first Rodenstock. I'll trade the distortion for the speed and sharpness.
Hope that helps.