AAM - MultiConnect and common objects

So you've read what Multi-connect does? It increases the number of domains in use by a page in a browser, which in turn increases the number of concurrent TCP connections from the browser to the server, potentially increasing the speed at which your page downloads.

If you have a reasonable expectation that your users will be on high bandwidth connections, and your application developers don't have the knowledge or inclination to add a CDN content-domain to the application, I would say enable it (in general - there are some exceptions). We use it on most of our sites on which we use WAM (the AAM precursor) - increasing the number of domains is a recognised acceleration technique.

Note that you will need to configure the number of sub-domains to use in another section (not sure where in AAM - I'm going to configure my first AAM next week) and also ensure that those domains resolve in DNS.