I received this lens on March 25, 2008. My first impression, was that it felt heavier than the kit lens. It was much better built, and had a metal mount. The lens hood was a nice addition. I purchased it for full price.
When I first tried it out, it focused quickly, but I didn't expect or see and improvement. Speed is perfectly fine. SSM would've been nice, but very expensive.
At f/1.4, there was no noticeable vignetting, and no visible distortion. At this aperture, it was a little soft, but much sharper compared to the kit lens at f/3.5. It's still sharp in the center, but has soft corners. It is although very usable.
At f/2, the lens get sharper, but not by much. The center sharpness spreads towards the corners, but not a whole lot. All vignetting (in tests) were not non-existent.
At f/2.8 is where the lens gets to it's sweet spot. The corners were marginally sharper than at f/1.4, but not impressive. Here, it is usab;e in almost any situation.
From f/3.5 and up, I have absolutely no complaints. It's very good from here and up, but what's the purpose of the wide apertures?
This lens performs great against flaring. In all of my photos in direct sunlight, there was no flaring as far I could see. With the lens hood, this is greatly improved when the sun is in the corner of the frame.
Bokeh is absolutely beautiful as expected from a large aperture lens. It is very smooth at f/1.4, but is slightly better at f/2. The circular aperture is a huge plus.
Chromatic abberation, I have seen none of. Purple fringing can be seen at f/2.8, but that was my only test.
From an amateurs standpoint, this lens is a must have if you can afford it. If you're on a budget, the Minolta 50mm f/1.7 is another great option, but it is certainly not better than the Sony.
The only thing I could ask for is:
A cheaper price (Canon is $25 cheaper)
Better build (Canon is much better built, but I can't complain)
SSM would be nice (Again, Canon has the better prime)
(They're all edited obviously)
^Photo above was at 1/4000 and -2EV, Aperture Priority.
Thanks for your time.