All I know is that in the Mac-only beta, all images must be in a single folder (and various sub-folders.) It's a little like iTunes. If you have a large number of files, and have them distributed across several hard drives and/or various locations on your network, you're SOL. My understanding is that Apple wants to position Aperture as a product for serious hobbyists and professionals, so I hope they enable the system to deal with multiple locations.
Aperture is a great program. I've had the opportunity to use it myself on occasion, and it is a great too for organizing all your photos if you shoot a lot of digital.
As for the thing about only storing photos in one place, I see that as a good thing. That way the program can work efficiently since it knows where all the images are located. Also, this helps the user because it makes backing up a simple matter (even though Aperture has its own efficient backup system built in; it will let you copy your entire library to a separate HD or burn specific images onto a CD/DVD for backup). If you have images stored in a separate location that you want to add to your aperture library, all you have to do is drag them in and it will copy them to the library.
The main downside I see to the program is its speed; it's really not worth using if you don't have a fast mac (i.e. a fairly new G5 or Core Duo mac)
Also, Aperture is not a beta. It's at version 1.1.
i've heard mixed things about this one. first, i heard that it was an incredible program with lots of great organizational and handy editing tools. but the more i researched it the more i heard negative comments about it. I heard it was slow, and basically a memory and cpu hog because it has such a hefty graphical interface. I also heard that there were some bugs in it, as its sponsor famous wedding photographer Joe Buissinik was greatly dissapointed in it at first. Something about him making the company change some things about it because he disliked it so much...I dont know, i couldnt find that again online, so it might just be some wierd rumor.
IMO, if you have CS2 and bridge, there is no need to get aperture as those two together make an incredible editing/file viewing combo.