The new Google Maps introduced a number of features, but I've been having trouble with it in Firefox on my aging MacBook Pro. When I scroll on a map, the map stutters and fades to black and takes more than a couple seconds to redraw itself. It's a less than ideal situation. Thankfully, there is a way to return to what Google calls classic Google Maps.
From the menu in the bottom-right corner of the screen, click on the question mark button and you'll be greeted with a menu with a link to Return to classic Google Maps. It will then ask you for feedback about your decision, and topping the list is Map display issues. You can check one of the boxes or not and click the Return to classic Google Maps link again to reload the page with the previous version. After the page reloads, you'll be asked in a thin yellow banner at the top whether you'd like Google to remember your preference for the classic version on your next visit.
There is, however, a URL that will take you directly to classic Google Maps, as discovered by Alex Chitu on his Google Operating System blog. To go direct to classic Google Maps, enter this URL:
It won't offer to remember your choice of maps for subsequent visits, but it makes for a handy bookmark.