I just spent the last two hours downloading and trying every CSV importer plugin that came up when I did a search for "CSV" in the Plugin directory. I couldn't get any to work and was about to give up, but way down on the list of results I saw this plugin, WP CSV, so I took a chance and believe it or not, this is the only CSV plugin I was able to make work!
The key to why this plugin is the best is simple: the "Quickstart Guide" the plugin author provides. It's simple, to the point and easy to follow. I'm actually amazed the other CSV plugins don't include such simple instructions.
This plugin will save me hours of time in manually inputing post data and custom fields info. I just did a test and was so happy to see my WP blog populated with some test posts that came from a CSV file.
So if you need to import some CSV data, download this plugin, read the Quickstart Guide and then figure out what you're going to do with all your free time!