Utility for Data Synchronization. MS SyncToy v Third Party

I use a large external HD USB 2 for data backup and I am looking for a good, user friendly, preferably free tool for synchronizing selected folders/files from my internal to the external HD.

The obvious choice would be Microsoft’s SyncToy 2.0, but is there a better tool by another supplier?

The requirements are that it should be
user-friendly and
do directory/folder/subfolder/file synch
including renames and deletes
fully or incrementally
on demand or automatically on shutdown.

see http://www.techspot.com/vb/topic53686.html

I love it

Thanks for a prompt and full answer jobeard, I shall follow your recommendation.

I’ve chosen the latest portable version Allway Sync 'n' Go 9.1.7, which I’ll “install” on my external HDD. It appears this is the best choice when you mainly synchronize between internal and external drives as in my case.

Info & download: http://allwaysync.com/ngo.html