We are currently using Symitar (Episys) which is a Jack Henry product as our core system. They offer their own CRM product, Synapsys. This does integrate nicely with the core. I honestly believe to have a successful CRM, it should integrate to provide ease of use. The biggest challenge we have found is similar to owning a smart phone, you can have it for years and uncover it has all of these cool features you didn't realize existed. You have to have individuals who are willing to "own" the CRM and consistently look for ways to get the most out of the product you are paying for.
We use ours in a variety of ways, but initially and most robustly use it for member follow up (Service Events). You can set service level standards for follow up and it provides great reporting. It can also be used for referrals, sales campaigns and profitability. A good CRM program is an elephant and you have to be careful not to try to eat it all at once.
Best of luck in your quest for the right CRM for your credit union. Please feel free to reach out if you have any questions.