I'm weighing the prospects of upgrading. I switched over to LR for two basic reasons.
First as apple's perceived inattention to aperture due to the lack of updates. This is still a concern, their track record is do a major upgrade and then infrequent updates. RAW support is similar.
Second issue was the localized non destructive editing.
One thing I missed when I switched over to LR was Aperture's tight integration with apple's other stuff. I could easily keep pictures on my iPhone, import them into iWeb even into RapidWeaver which isn't even an apple product.
I do like how LR displays the grid of images in the library module. I can see the image name, date, index # and the rating. With aperture I need to switch over to the metadata tab and then I only see the info on one image.
Overall however I like aperture's clean interface much better and how it organizes the images over LRs.
I'm about 85 - 90% sure I'll switch back and given the low price of the upgrade, it makes the decision easier. I mistakenly purchased an OEM copy of LR2 while legal, I cannot upgrade that, so I'll be on the hook for the full price - another reason why switching makes more sense.