There are introductory videos on the Aperture Support page: http://www.apple.com/support/aperture/
Also look at the online version of the Aperture User manual:
And Kirby Krieger's recommendations here:
. I am not sure that I understand the advantages of tagging metadata but presumably a tutorial should be available somewhere.
You can have hierarchical keywords:
For example for nature photos you may want to tag your photos with keywords like "Animals" and "Plants", and within the "Animals" categorie you want "Birds" and "Cats", within the "Birds" categories "Waterfowl" and "Songbirds".
In Aperture you set up the a hierarchy:
Now, If you tag an image with the keyboard "Sparrow", it will automatically included in all searches for "Songbirds", "Birds", and "Animals" as well.
You can search for all kinds of EXIF or IPTC tags, and define presets of metadata, that should be applied automatically when importing into Aperture. Defining presets is what you will be doing for all aspects of managing your photos. You can customize your workspace and the tools you are using. For example, if you find that your raw photos are all underexposed, because you have set the camera to preserve highlights, you can define an import prset to automatically increase the exposure on imort.
In iPhoto you may find it difficult to drag between events, because only one event ca be viewed at a time. In Aperture you can open browsers for more than one project (event) or album.
Just have a look at the documents at the Aperture Support page.