I've sold all my other Pentax 50mms, including the FA version, and kept the best of the lot. This one is built better than the FA version (more metal) and focusing has been spot on with my Pentax digitals. I've sold many a landscape taken with this lens.
A lot of people recommend getting the 1.4 and 1.7, but it really depends on what you're going to be using it for. I've owned an embarassing number of Pentax 50mm lenses, and I've never been able to seperate the prints from different lenses. When I know I might be making larger prints, I use my "best" 50mm lens, but that's for my confidence not because I've ever been able to tell.
Pentax DA 50mm f/1.8 medium telephoto lens : Pentax Ricoh Imaging announce the introduction of its new smc Pentax-DA 50mm f/1.8 medium-telephoto autofocus lens, which is designed exclusively for use with the company’s K-mount interchangeable-lens (ILC) digital cameras. Thanks to state-of-the-art optical design technology from Pentax, the lens’ image coverage is optimized for Pentax K-mount ILC cameras to deliver sharp, clear images from edge to edge. With a sleek, modern look and a lightweight body, the new Pentax-DA 50mm f/1.8 lens was designed with versatility and flexibility in mind and is ideal for photographers of varying levels, from amateurs to professionals.|
If we are talking about the 50mm f2 A, it is sharper than zooms in this range but its not as impressive as other Pentax 50mm's. That said it is still a very fine lens. It was actually my first K mount prime, but after getting both the f1.4 and 1.7 A lenses it seemed a tad redundant.
Don’t be fooled by their modest price tag – lenses are great! I have the pleasure to own a few old Pentax Spotmatic cameras and lenses – they are all great. Both the build quality and the image results are superb. Takumar lenses tend to be less expensive than their more collectible Carl Zeiss competitors. The 50mm 1.4 was designed as a competitor to the Carl Zeiss and lenses. The Takumar 50mm 1.4 was sold with the Pentax Spotmatic cameras. Apparently Takumar lost money on every single copy of the lens they sold when it was introduced. Therefore, they later replaced the early 6 element lens with a newer (and cheaper to manufacture) version. Note that there is also a Pentax Takumar 50mm 1.8 lens.