I'm not a professional photographer by any means, but I did recently purchase an Olympus PEN mini E-PM2 micro four thirds camera. I read reviews on this lens and bought it before I went on my 2 week European vacation.
This lens is definitely worth getting. I used this lens probably in about 80% of my shots. Since it is a pancake lens I left it on my camera as it's main lens. It was like having a point and shoot camera, ready to use at any time.
The photos it takes are spectacular. I've always been wondering how people can take such great photos, and its by having great lens like this one.
The low light performance, something that I was searching, for is spectacular. Only negative is that in low light conditions and paired with an Olympus micro 4/3 camera it does tend to search on the auto focus. Sometimes it takes 3 to 4 seconds to auto focus. Many other people have spoken about this and it is in fact there. But for me I'm not taking fast shots in low light so it is manageable. I did not use it to shoot video.
It is pricey but if you are in the digital photography for a hobby, it just goes with the territory. I wasn't sure if I was going to be satisfied spending the amount I did for the lens, but after my vacation and seeing the shots I was able to take, it was worth it for me.