Can nodes created using Feeds be updated automatically? The Feeds documentation mentions that it's possible to import a CSV feed and create nodes from it, assigning column values as CCK fields, but it doesn't mention if it's possible to update nodes when those values change in an updated feed. Is this possible to do using Feeds or an additional module?

For example, a feed is downloaded in week1, creating a node for a Red Widget. Its price is £10.

In week2, the feed is updated with a new price of £12 for the Red Widget.

Can the node initially created be updated with that new price without importing a new or duplicate node?
I believe as long as you have a primary/unique ID for each item in your CSV this should be very easy to do with the Feeds module.  When you do not have primary key to work with things get tough.