Having read most of the posts, I think that there is a lot of disinformation about Aperture. As Steve said, it is not a replacement for Photoshop. (There is definitely a possibility that he was trying to pull Adobe's chain , however)
As to workflow, Aperture is quite good. Most important feature is that the "negative" - your original RAW file is never mucked with. Anything you do, from correcting the exposure, to tweeking the temperature of your photo is recorded only as an incremental change, so you do not get several different "full" versions of your work. The key is to "get it right" in the camera vs "I can fix it in Photoshop."
If you need to do cutouts and montages, sure you still have to use Photoshop. It is, in fact, an extremely powerful tool for manipulating images. Anything this powerful is not going to be totally intuitive to operate, so RTFM, go to the PS seminars and learn how to harness the power.
Where I see the strength of Aperture is in organizing, ranking and "touching up" your RAW photos and then being able to quickly output a web gallery, for proofs to a client, or printing with most of the settings handled by Aperture.
It is really easy to "recover" a RAW file from the Aperture Library .. just Export the Master file. Backups are handled to your designated "Vault".
Missing: Teathered shooting. At present, I still have to use Nikon Capture to have my G5 and D2X "talk" to each other. Maybe version 1.2 will get this feature added.
This is my first post here, so take it for what it is worth.