I know this might be controversial and I'm not trying to stir up the ages old Aperture vs Lightroom debate, but I imagine there are other reasons for the price change other than Aperture, and I imagine the same price point will be applied on the Windows version where Aperture does not exist.
I have used both pieces of software (I now use iPhoto) and I have to say that while LR bugged me with some things it did, Aperture had far more significant problems. When I got Aperture it had added photo books support, and it was so buggy and slow that it was literally impossible to use without having it crash after long periods of beachballs. Updates came and did not address it, after a while I suppose it was fixed but I had certainly lost interest at that point. Sharing photos was/(still is?) pathetically complicated. The performance of the whole suite was ridiculously poor. The machine I used Aperture on (same as LR) was 2.4ghz MBP with 8GB of RAM and the photo library was large-ish but <50GB. None of this happened with any version or BETA of LR .. far from being an Adobe fan, I at least respect that they do reasonable verification of their software that they sell (for insane pricing)
The performance difference was very start in Aperture 1.0 vs Lightroom 1.0, but honestly I haven't seen any noticable performance difference with more recent versions of Aperture and Lightroom.
For me, the modality of Lightroom was the killer that pushed me back to the (then-slow) Aperture. The modalitity has been somewhat alleviated in more recent versions, but Lightroom still has a quite obvious "This Is How You Will Work" workflow which works far better than the way I actually want to work (whereas in Aperture the way I actually want to work is just as easy to do as the Lightroom Canonical Workflow is in Lightroom).
IMHO, the remaining clear advantage for Lightroom is the integration with Photoshop. If you have Photoshop and feel the need to send some reasonable number of your photos through that tool, Lightroom provides a better workflow than Aperture. I personally only use Photoshop (Elements, because I'd much rather spend the $800/year on lenses than on Photoshop CS) rarely, so Apertures export/import hoops don't end up bothering me very often. But, I can definitely see someone doing that every day would not want to suffer through Aperture's workflow.
The downsides: severe favoring of a Canonical Workflow, price, Adobe-isms, etc.
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To be fair, Photoshop Elements is a great product for non-pro users & is priced very reasonably.
Well, "great" is a bit of a stretch, and "reasonably" is still well above the better-featured competitors. But, it's something to consider, along with Pixelmator, Acorn, etc. IMHO, it reeks of "My First Photo Editor" way too much; I feel like I need to lower my IQ by 30 points when the PSE icon starts bouncing in the dock.