Win. 231 is fine for the .38 Special, .45 ACP and lighter loads in the .357 Mag. I started using it exactly for the same reasons--Unique wouldn't meter uniformly through a RCBS Uniflow measure.
I use 231 behind 158 lead SWCs for .38 Special loads. I've been using 4.7 grains. I've also loaded 200-grain SWC .45 ACP target loads--4.7 up to 5.0 grains depending on the pistol. It's also a great powder for 9mm loads.
You also might look at Hodgdon Universal. It burns at about the same rate as Unique and 231.
I did try 231 in the .45 Colt a few times. It didn't work as well as Unique--the standard deviation was high. I figured there was too much room in the big case.