So what are some of the alternatives everyone has moved over to?
I continued with Aperture for just over a year after they announced they were ceasing development. A new camera forced the change in the end. I tried out trials of C1P, Exposure and Lightroom.
C1P produced excellent results, but the learning curve was too steep for me and at that moment in time I didn't have time to persevere (a friend and colleague did persevere and he hasn't looked back). Exposure was lacking several functions that were important to me. So I went with Lightroom...
However, I never felt at one with Lightroom for a number of reasons, I always wished I was still using Aperture. I now also use Photo Mechanic for image culling, it is so much quicker than culling in Lightroom.
I trialed Exposure X4 (4th gen. of Exposure) at Christmas and found a good range of features and enhancements had been added since I first trialed it. I also really, really like the folder based image view workflow (as opposed to file import based workflow). Anyway, I ended up buying it and I'm still loving it. Their customer support is incredible too - a reply is received typically within a few hours of sending my question. I still use Photo Mechanic for image culling.
I have since also trialed FastRawViewer for culling images, and it is definitely a very good alternative to Photo Mechanic (it is also considerably cheaper). It is definitely worth trialling both PM and PRV if you don't already own either imo.
I still miss Aperture. My ideal would be culling in PM and editing in Aperture 4/5 (if only they existed!)