Summary: This is a great lens and costs a great deal less than others similar to it. Let's do the "not so great" first and get that out of the way. It isn't the fastest lens around and it has been around a while and could use an update...OK, that does it for the negative in my experience. Now for the good...and there's a lot of "good" in this lens.
Summary: Plusses on this lens: very fast, nice workable focal length, small and light, good build. Minuses: lack of sharpness wide open, bokeh only so-so. Sony has made a great lens for the money with the 50mm 1.4. Stop it up to 2.0 and you get great sharpness and contrast across the frame. The 50mm focal length translates to 75mm with APS-C, making it a slight telephoto, although perspective distortion is minimal.
Summary: This lens is perfect for portrait photos. Combined with the HVL-F43AM flash it produces close to perfect images with the Sony A850 body. The low apature f/1.4 allows you to focus on the object and blur the background. The lens is full frame (35mm) and allows you to use the full 24Mega pixel of the Sony A850/A900. There are loads of professional alternatives to this lens, but this is just very good value for money.
Excerpt: I don't have any negative feedback to offer on this lens. As close to negative as I can get is there's no SSM focusing, but that would cost more anyway so it seems to be a fair trade off. For the price it's an excellent piece of equipment that is necessary for anyone wanting to take their photography to the next level. f1.4... I love you! It's wonderful to be able to hand hold action shots all the way till dusk without cranking the ISO up.
Summary: Got this lens as an update from an old Minolta prime, wanted the best possible 50 for my full frame. It has excellent center sharpness, even wide open, and the corners aren't too bad either. Build quality is solid but unspectacular. Focus is fast and accurate, which is an improvement over the old. Color is on par with several of my old Minoltas(thats good)but CA very bad at 1.4-2.0 on my copy, which is disappointing.
Summary: I'm happy with the speed of this lens, which I'm using on an A550. There are a lot of good things to say about the lens (check the web reviews for details). However, the autofocus is slightly off at full aperture. I scrutinised three lenses in the store and they all had the same problem. Basically if I focus on the nose the eyes will be sharp. This is not really acceptable, but I'm told it is possible to hand in the camera and lens to Sony for calibration.