Just to let you guys know, the scroll box is up, but it isn't yet implemented on all styles (the styles that have custom postbits). I can't go through all the styles to check, but the vBulletin Default style has the scrollbox.
One of the reasons we decided to have scrollboxes there was to make it easier to know if your signature falls within restrictions, and eliminate the need to use this thread to ask if it does or doesn't. Just remember that if you're considering replying asking if your signature is within these new limits. While it isn't against the rules, you now have a sure-fire way to know if it is or isn't within the rules because of the scrollbox if you're using the appropriate forum style.
There's still a few days before this is enforced, and by that time, they'll be sure to be updated on all the styles that don't have the scrollbox up yet. But until then, switching to the vBulletin Default style and just looking at your signature area for a scrollbox (or scrolling on the signature for one to appear, depending on your system settings and operating system), you can see if it's within the limits or not.