About 2 months ago, I had to evaluate MOSS / WSS - compare its features and capacity plan. I'm not sure i want I to go down the Sharepoint path - Its too restrictive, too meta-programmy , it doesnt give you OOTB AJAX enabled WebParts, and is a different path than Silverlight (maybe the next version will be SilverPoint ?). On the flipside, the concepts of pluggable WebParts, InfoPath, Excel Services and Sharepoint Workflows are appealing.
Basically, to learn sharepoint you have to read the following: