The GD designation is, unfortunately, mostly a memory - and even when GD code was available it tended to be a year or two behind in (usually critical) features. Even ED vs LD isn't 100% indicative of ideal code versions in all cases.
Bugs can exist in any version. The bugs that involve your particular set of features are the ones you care about. Check out the bug navigator to list the open/fixed issues in the version of code that best fits your requirement. Your Cisco SE / support team should also be in a position to run through a quick bug scrub to see what the prevailing wisdom is as far as best of the latest-and-greatest but ultimately the bug toolkit is the best tool you've got.
As to upgrading from 12.2 - what features would you gain that would be particularly helpful? Some shops I've seen have made the move to be able to support SSH certs or new knobs on routing protocols while others just want to be on a reasonably modern rev just as a maintenance practice. Toward this end you might also want to run through the feature navigator to determine exactly what's changed from version to version.