First off, I should say I've no experience with any other ultra-wide rectilinear lenses.
I quite enjoy my DA14mm. Part of the reason I went for it over the DA15 was the higher magnification at close distances. It's great for environmental type portraits of reasonably little things. I find it plenty sharp up close, even wide open.
It's generally pretty well priced on the used market, I might have been swayed to the DA15mm if I had to buy it new.
It's my biggest lens, but it's still not
that big unless you compare it to the tiny pancake types. Solid and well built.
At some point I plan to get an underwater bag type thingie and I had expected the f/2.8 would be especially handy. Unfortunately the funds I had for this got gobbled up when a da10-17mm appeared locally a few months ago, so maybe next spring
.
It can flare with the sun in the frame, oh yes. I don't really mind though, the sun is rarely a part of my compositions and the flare can be pretty trippy at the correct angles.