We have also made some improvements to the importer framework. Notably it is now possible to perform amulti-process importin order to make better use of multi-core processors. If you run an import via the CLI and you add the --processes option with a value greater than 1, then multiple PHP processes will be used to perform the import, instead of a single CPU core being used as is the PHP default. Your results may vary, but with the number of processes set to equal the number of physical cores on a sufficiently powerful server, you should notice a significant increase in performance.
You can also run your import command with the new --finalize option which will run the finalize stage automatically after the data import has finished.