When Apple announced their free iCloud service at WWDC 2011, users of the previous, paid, MobileMe service were given a temporary boost in storage. The extra storage was previously set to expire in June of 2012. According to a recent change in Apple's MobileMe to iCloud transition FAQ, however, that's now been extended until September.
MobileMe members with 20GB of purchased storage receive a complimentary iCloud storage upgrade of 20GB, and accounts with additional purchased storage (40GB to 60GB) receive a complimentary upgrade of 50GB after moving to iCloud. These free upgrades are good through September 30th, 2012. After that date, you can continue the upgrade at the regular price or let it expire and use the free 5GB plan.
The extra storage is meant as a way to encourage MobileMe users to transition to iCloud faster -- as is the recent offer of a free OS X Snow Leopard upgrade for OS X Leopard users.
While Photo Stream and iTunes in the Cloud don't count towards the iCloud storage limits, mail, Documents in the Cloud, and backups do. If you're currently enjoying the extra storage Apple provides MobileMe users, you have several extra months to enjoy it. After that, you'll have to decide if you want to keep paying for it or not.
There are several ways to cut down on the amount of storage you're using -- especially turning off Camera Roll backup. Check out the iCloud links below for more.