I have the Uniflow with the small insert. Unique goes through the meter fine -- there's no resistance when cutting a flake, for example. However, there is, for me, more variation in the weights thrown with Unique than with a ball (or ovoid) powder.
With Unique, I'd get one throw a tenth high, one throw a tenth low, two that were right one, one high, etc. A tenth of a grain either way isn't going to hurt accuracy, I don't think, but it did make setting up the meter something of a pain in the behind: I'd have to throw 10 and take the average to see what weight my measure was throwing.
For no other reason than because it makes the measure easier to set up, I switched to ball powders. I do miss the smell of Unique, though. That powder has the best smell when it burns.
