It was the first powder I ever loaded, so I don't know. It's fast, but not as fast as Clays.
Unique is a fairly good analog for Universal Clays. I don't know about Unique (only used it in Houston, where temperature was always warm to hot), and I don't have crono data to back this up, but Universal Clays _seems_ to loose a lite bit of power on cold days. My sub-minor steel load would work fine at the indoor range, but fail to cycle the gun on cold outdoor days (40 degrees or below). I typically use light oil over grease, so I don't think lubricant viscosity was a contributing factor.
http://www.hodgdon.com/burn-rate.html