What my mate said...
Fantastic presentation from two Apple guys probably helped but, and I hate to say it, it was all so intuitive. You at last have a full light table and loupe setup. By full I mean a huge workspace where you can group slides together (stacking as Apple calls it). Either automagically based on timestamp/bracketing mode, or just by grouping them yourself. Brilliant for those shots where you burn the equivalent of a roll of film just to get *the* shot. So, you have these stacks of images that you can dynamically expand/contract on the lightbox, line up side by side etc. And then you have just the most amazing implementation of a digital loupe you can imagine. Utterly jaw-dropping, caused spontaneous applause from an audience primarily composed of non-Apple zealot pro photographers.
The other feature I really liked was their method for applying raw image adjustments - very visual, none of that batch conversion bollocks (although you can do that in the background if you wish), very fast, very easy to do side-by-side comparisons of before and afters.
Also some nice project management options - one-click archive/backup, a really well implemented album creation feature (including the ability to do any adjustment you would do elsewhere in the image actually on the page itself). Seamless (and I really mean seamless) integration with Photoshop and of course all this processing is non-destructive - differently implemented to Capture as you never (unless you want to) save your image adjustments to the source file.
There's a whole bunch of other stuff I've forgotten that was also ubercool, a lot of which is also in Capture. Imagine Capture with a few hardware-specific features deleted (eg. CA correction, image dust-off (although Apple's implementation for that is better), fisheye correction), with a lot of stuff added and the whole thing given an engine transplant, twincharged, and then NOSed to the maximum.
Yours for £349, you probably won't need Photoshop ever again, all the obvious tools are in Aperture...
Quite simply the most stunning piece of new software I've ever seen. An over-used term, but its a quantum leap - the biggest since Photoshop arrived...