I was just reading a thread on Apple's support forum asking people the "Aperture or Lightroom" question.

Here's my 2 cents that I added to the discussion:

I started using Aperture the day it was released. I became somewhat of an Aperture evangelist, I blogged about it, talked about it on my podcast and became an author on O'Reilly Media's "Inside Aperture" blog.

...However about 3 months ago I bought Lightroom and gave it a try. As of a few days ago I have totally made the switch from Aperture to Lightroom. There are certainly things in both programs that make them fantastic pieces of software and now that I'm a Lightroom guy there are a few features in Aperture that I miss but in the end I made the switch for one main reason: In Aperture I always had the feeling that I was doing a chore, what I was doing in Aperture felt like something that was required of me after a shoot ... in Lightroom I have a totally different feeling, I feel like during the entire post processing phase I am being creative, it's more of an extension of the creative process of photography and I feel like there is more I can do within Lightroom and therefore I think I get better results as opposed to just cataloging and rating shots. I know that's not a technical review of the products strengths and weaknesses, but in the end what really matters is how the software helps or hinders your creative process and frankly I feel a lot more creative since switching to Lightroom.

The bottom line (for me) is that I think my photos look better now that I've switched to Lightroom and I'm having more fun working on them. Sure, tasks like rating, keywording, etc are still a bummer but the rest of it is more fun and that matters to me.