SPContentLoader is a tool to upload test documents to a Sharepoint 2010 site.
It will use a local folder as source and will randomize all content types, choice fields and enterprise metadata fields.
It was used to upload 1 million records to a single document library !
SPContentLoader "Source Folder" "Destination Document Library" NumberOfDocuments
Bear in mind this is IT PRO code :)
I've done some limited testing but it worked for my purpose...
You are welcome to improve it, fix it and add new features.
If you are doing some MASSIVE loading, remember to rebuild or reorganize indexes on a regular basis. Otherwise you will experience decreasing performance.