Salesforce has mostly implemented their security changes. FYI, this is the help file page explaining to admins how to setup Network Access in the application and what happens when a user logs in.
If you have an org that you need access to without the burden of this restriction (e.g. an org you use to perform demos at various locations and/or from many different computers where you might not have email access), you can authorize all IPs by making 0.0.0.0 the start IP and 255.255.255.255 the end IP in a Network Access record.
Doing this will essentially put that org’s security back to what it was before Salesforce made their enhancements. I wouldn’t recommend making this change unless you actually need it, but it can come in handy even if for a short-term fix.
This is the approach Salesforce.com has taken for Test Drive orgs on AppExchange listings so that Test Drive users are not restricted access to a demo. All of my Test Drives had a record with this range pre-populated by Salesforce when they made their security changes.
Note: I do not recommend anyone do this for their corporate Salesforce.com org as this would negate all the good work Salesforce has done to button things up.