Gmail's Google+ Interstitial

Google works hard to convince people to join Google+. I went to Gmail, signed in using an account that hasn't switched to Google+ and got this interstitial page (the URL starts with "https://plus.google.com/up/accounts/inter"):

"Update your account. Create a public Google+ profile and get great new features in Gmail."

You only have to check "I understand the changes to Picasa Web Albums when I create a profile" and click "Update and continue to Gmail". For now, you can ignore this page and click "not now, continue to Gmail".