Back in the days of film, I had a Zeiss 25 mm f/2.8, which I quite enjoyed. Then with my Pentax K10D that lens got converted to a 37 mm equivalent. Even though that is a quite versatile focal length, every once in a while I missed working with a wider lens. That's why I could not resist when Panasonic launched the Lumix 14 mm f/2.5 for Micro Four Thirds cameras, a wide angle lens that is equivalent to 28 mm. It is a beautiful little pancake, even smaller than the 20 mm f/1.7. The E-P2 becomes even more compact with this lens on.
However, some of the reviews so far don't seem to be so enthusiastic about this new 14 mm as they were about the 20 mm. Vignetting at large apertures, distortion and low border sharpness have been pointed out as being significant. So, what's my humble opinion so far? The lens is well built, compact and fast focusing. Vignetting can be used for aesthetic purposes or software corrected when undesired, distortion is only really critical in architectural photography, and border sharpness has never been a key factor for deciding the quality of a photo*. I'm much more concerned with relearning how to compose with a wide angle lens than with optical performance technicalities.
Olympus E-P2 + Panasonic Lumix 14/2.5
* Concerning the (ir)relevance of optical sharpness when evaluating the quality of a lens, Ken Rockwell posted this interesting (and polemical) article in 2008.