Originally posted by juristkostya this means that I use it in such a way that avoids weaknesses :-)
But there are weaknesses, and they are significant.
I already had the Samyang 14mm f2.8 and whilst sharper over the whole frame, faster and sharp at f2.8 it had significantly more 'significant' weaknesses than the DA15. Lens flare, distortion, colours, rendering, sun burst shape, size, weight, close up ability and every other lens quality were significantly worse.
DA15 has pixie dust and buckets of it, I bought it for a photography holiday down the west coast of Ireland which is photography paradise and managed to nail some of my best ever work and haven't left the house without it since.
I only use the Samyang for astrophotography which it is great for and the weaknesses don't really matter.
Shows the reason why you may need 2 prime UWA lenses, one for day and one for night with different specialisms.
You could have a DFA 15-30 that does both but then a massive weakness shows up, that being the huge beast it is.
A Canon shooter thought I was using a compact camera up the mountains when it was K-30 & DA15, he couldn't believe it was a DSLR and UWA.