ImportWP Version 0.6 update adds a major speed boost to CSV Imports along with some small interface tweaks and minor bug fixes.
Speed Improvements for CSV Imports
During a recent performance analysis of ImportWP’s WordPress CSV Importer we noticed that during an import its takes time for the importer to load and unload before and after importing each record, this update has reduced this time by using a single process to bulk import multiple records at a time. Looking into further areas where we can reduce time i noticed that the slowest part of importing multiple record is the fact there is no method within WordPress to bulk insert/update records, without having to write custom methods to achieve this, but in doing so it will be difficult to accomplish this and keep the same data integrity that you get from using core WordPress methods. In the future we may replace these methods, allowing us to interact with the database directly but right now this is not a high priority.
With the latest CSV Speed improvements we have updated the interface slightly, hiding the importer history until it has been complete, but sill showing progress during the import. Pagination has been added to the importer history screens to speed up page load times for large imports.