As this is a new 50mm, I am tempted to compare it vs. newer designs in its class, e.g., the Sigma 50/1.4.
According to photozone and test shots I have seen, the Sigma 50/1.4 outperforms a reference design like the Zeiss 50/1.4 in three points:
- Same (better than excellent) center resolution, almost best at f/2.8 already.
- Same (very good) center resolution fully open.
- Better (very good) border resolution fully open.
- Same nice (disk-like rather than circular-like) bokeh.
- Better CA wide open.
- Better contrast around light sources (less glare).
The FA43 isn't on par, esp. in points (2.), (3.). And from the images, the DA*55 doesn't seem to be on par in points (2.), (3.) and (4.).
It would be interesting to compare the DA*55 vs. the Sigma 50/1.4 in the other 3 points as well. The DA*55 may still be a very strong contender.
To verify that point (1.) is met: two 100% crops, one at f/2.8, another at f/4, of a high contrast subject (like a magazine page pinned to a wall 3m away) would do the job: Good if no difference is visible, bad otherwise.
To evaluate point (6.), it would be great to see an outdoor night shot fully open (with street lamps, bright distant windows etc.).
EDIT:
It would be great too, to know if any of those lenses have significant spherical abberation. As it is awkward to properly focus a lens which has.
EDIT2:
To set things into perspective...
Pentax FA50/1.4: 196g
Zeiss 50/1.4: 330g
Pentax DA*55/1.4: 375g
Sigma 50/1.4: 505g