FA50 is very soft on the larger apertures. It actually needs F5.6 or F8 to get very sharp. This even causes problems for the AF system, and it is known to be one of the slowest focusing lenses. When adding the shallow DOF for the larger apertures, this is a difficult lens to use sometimes. Having said all this, the FA50 is still a great lens, and has been one of my favourites for over 10 years. A colensuple of weeks ago I got the DA55, and that is my new fav lens in this focal length. It is also soft at 1.4, but not as soft as FA50, and at 1.7 it is already very sharp.
I should also add that with sharp I talk about pixel sharpness as shot on a K20. I would say that on a 6Mp camera the difference between FA50 and DA55 is probably much smaller, but on K20 it is huge. This is of course still not important unless you are going to print pictures in very large size.
So FA50 is a great lens, but if you are looking for super sharpness (pixel peepable) you should shoot at F5.6 as a minimum. Using F1.4 at close distance is difficult with any lens as the DOF is some 4-5 mm at 50 cm. You need to take lots of pictures an as long as you are not too stable on your feet, hopefully some of them will have the sharpness where you want it.
Here is a URL with a test I did between FA50 and DA55, not so much text,. and all in swedish. Test only looks at center sharpness so far, even though I have looked at edge sharpness and bokeh to some extent.
http://www.fotosidan.se/forum/showthread.php?t=109251 FA is the first of each pair of pictures, DA the second. All 100% crop on K20D.