I have been a Photoshop user since v2 for Windows. Back in 1996. I love it and know it like the back of my hand. I have Adobe CS3 for Windows and have it installed on my Bootcamp'd Win7 install along with some other video processing apps that are not Mac compatible. For hard core editing of photos, I will always use CS3. I have my own filing system for photos and dont need a photo library management app.
Now, that being said, I threw down the $80 for Aperture last week. I added (for testing) a bunch of photos from my last Scotland trip; 1200 give or take. I sat with Aperture and have gone through and fixed horizons and some color correcting in quite a few, including reballancing of the luminosity of the purposefully underexposed landscapes that were taken to preserve cloud cover. While I was able to do this pretty easily (most of the apps out there work the same when you get down into the meat of them) there were some things I missed. While doing the luminosity editing in levels, I miss the dropper to pick out Black, Gray, White points that is part of Photoshop. However, on the other hand, the fixing of the horizons was so easy in Aperture, I was quickly able to run through the whole 1200 in about 45 mins.
I got Aperture in order to make those quick edits on the fly for proofing and it is doing its job. Considering it is so much cheaper through the Mac App store than it was in the Apple Store or at the time I got my MBP, it was pretty much a no-brainer.
Will I replace Photoshop? Not on your life.
Will it make photo management easier? Yes, for quick edits.
Will it find its way into my daily workflow? I do not know yet, but a quick guess, no.