I've been using Unique for over 30 years. In the early years, it was used in my Ruger Blackhawk .45 Long Colt.
More recently it's been used for the .45 Auto in my Kimber Custom Classic Target: 6.0 grains under a 230 grain hard-cast lead roundnose, or full metal jacket. The same charge works for both, so I don't have to adjust the powder measure in my Dillon 550B progressive press.
I've also used it in the .38 Special, .32 Smith & Wesson Long, .25 Auto, .357 Magnum, .44 Special and .44 Magnum. And some lead plinking loads in the .32 Winchester Special and .45-70 rifles. Also a few times with the 12 and 20 gauge.
A most versatile powder!
It has its problems, though. Perhaps this only applies to the older Unique, I haven't tried the newer stuff yet.
In very cold temperatures --- 20 Fahrenheit or -7 Celsius --- or colder, when used in cases with large volumes such as the .45 Colt or .45-70, its ignition may be problematical.
I learned this in the early 1970s, while shooting outside of Spokane in 10 degree (-12 C) cold.
The first shot went BANG! The next shot went Foop! The third shot went Blap! Then a BANG again. I couldn't hit the can sitting on a stump because the velocity varied so much shot-to-shot, that my bullets were landing at different elevatons.
The stump showed a vertical line of bullet strikes, varying from near the bottom of the can to the bottom of the stump!
Later, I read about this characteristic of Unique in a gun magazine. But it only applies to very cold weather, with an equally cold gun and ammo (the ammo and gun had been stored in the trunk of a car overnight) in cases with large capacity.
If you carry your pistol in a shoulder holster under your coat in cold weather, where the ammo is kept warm by your body, it wouldn't be a problem. In fact, a shoulder holster is THE way to carry a pistol in cold weather. With a side holster, you often have to lift your coat out of the way to get access to a sidearm; not so with a shoulder holster.
In the .45 Auto, I don't believe ignition problems in cold weather would be a problem, owing to the much smaller volume of the case.
It may become a problem with very lights loads in the .38 Special and larger cases. And certainly might occur in the .45-70 with its cavernous capacity.
But perhaps the newer Unique no longer has this problem. I can't say. Just something to keep in mind if your ammo and gun will be exposed to sub-freezing temperatures.
I still use a lot of Unique. In the past few years it's been dismissed as dirty-burning and creating a lot of smoke. Frankly, I suspect that's due more to the bullet lubricant than the propellant. I don't recall ever having that problem with my Ruger .45 as long as I had a good crimp on the bullet.
But fail to get a good crimp and most propellants will durn birty ... er .. um .. burn dirty ... heh.
