FileMaker Inc. discontinued sales and support of FileMaker Go 11 some time ago, and FileMaker Pro 11 will follow soon. FileMaker Pro 11 is getting pretty long in the tooth. Don't wait until you're forced to, to upgrade to FileMaker Pro 13.
In particular, note that FileMaker Pro 11 is "not certified" by FileMaker Inc as compatible with the latest version of Mac OS X, version 10 "Yosemite." Yosemite wasn't even in beta when FileMaker 11 was developed.
As a practical matter, "Not certified" does not mean that FileMaker 11 and Yosemite are aggressively incompatible. In my experience, FileMaker 11 opens and generally runs fine in Yosemite, although there are a few small quirks and annoyances. (This page from Brown University's IT department claims that the even earlier version, FileMaker Pro 10, is compatible with Yosemite.) If you must upgrade to Yosemite and for some reason don't want to upgrade to FileMaker 13, odds are you and your databases will survive. But no promises! As always, be sure to make sure you're backing up your databases regularly.
Rucksack Texnology will cease FileMaker 11 development for CMAssistant as of the end of this month (December 2014). Acquittal was developed in FileMaker 13 from the get-go.
Keep in mind that you can buy FileMaker Pro 13 via a subscription at a very small price per month. It's like renting the software. To view the pricing (currently $9/month) https://store.filemaker.com/US/ENG/LIC/https://store.filemaker.com/US/ENG/LIC/
William Porter is Rucksack's owner and principal. He's been writing on a range of tech subjects for three decades. Yikes!