[bossa]

I've owned the fa50/1.4 and the Nokton 58/1.4. I sold them both after getting the DA*55/1.4. It's better than both of them. Wide open, the 55 is sharper and contrastier (which makes it look even sharper), and has better flare resistance than the Nokton, though I didn't see much over the FA50 in this regard.
I can't speak about the Stigma 50/1.4, as I've never been interested in their lenses.
My understanding from what I've gleaned off the net is that while it is quite sharp, it isn't as well built and is a bit of a flare monster.

Referring to a Sigma lens as a Stigma isn't all that funny for mine. Most Pentax users are probably grateful for the lens choices they offer even if they aren't always the best. I haven't had any major flare issues with my Sigma and, as far as it goes for me, it is on a par with my FA31 for most of what I use it for. I actually prefer it in a few ways, full-time manual focus being one of the main features.

If I didn't have to actually buy a lens to try it around here, I'd have some personal experience with the DA*55, so until I do that's my perspective.

[TOUGEFC]

I havent tried the Sigma 50mm, but the flare resistance on the Sigma 30mm is better than the DA15!

[Anvh]

The DA*50-135 is indeed a nice portrait lens, get that one instead to get some more flexibility, you can always get a 50 later.

One thing to look at is the bokeh of these lenses, i'm someone (and i ain't alone) that dislike the bokeh of the FA50 and DA*55 so personally i would go for the softer/smoother bokeh of the Sigma 50.
No idea how the other lenses are.

[krebsy75]

I also have the DA*55 and love taking portraits with it. It renders skin tones perfectly and the focal length is just right.

85mm is a bit long for indoor portraits , IMO.