There is a slight startup draw size issue in 4R2 which you can get around quite easily. If all you do is start ZBrush, draw a primative and start sculpting right away, you don’t have to worry about this issue. Otherwise…
If you have just started ZBrush 4R2, draw a Sphere3D on the canvas, turn on ‘Edit’ (T), turn off ‘Edit’ and then ‘Cntr+N’ to clear the canvas. Now your all set. If you already have the ZSphere chain started and are editing it, all you have to do is, while still in ‘Edit’ mode, click on the Sphere3D in the Tool palette to put it on the canvas and then re-select the ZSphere tool you were working on. Now draw size will work and remain working until you close ZBrush.
Note: I recorded a Macro to do this and made the Macro to run automatically when I start ZBrush (See my post here). This way, I don’t have to think or worry about it.
Note: If you start ZBrush 4R2 and immediately go into PaintStop, this will also happen. Just exit Paintstop, do the above, then re-enter PaintStop.