Posting in the Magento forums has been disabled pending the implementation of a new and improved forum solution which should better serve the community.
For new questions please post at magento.stackexchange.com, the community-run support site for the Magento community. We will be providing updates on the new forum solution soon. For questions or concerns please email firstname.lastname@example.org.
Why magento needs to get rid of the login/register step during checkout
The solution: remove the step completely and add an option to login and a checkbox to register at billing.phtml.
And while we’re talking about optimizing onepage checkout - the accordion layout is simply outdated, the multi address checkout has a much nicer look and something like that could be achieved with pure css so the loading times wouldn’t increase.