My opinion: The frigate's claim to be better than a Kestrel isn't exactly accurate — it only betters it in one category, shields. I prefer the Kestrel, but if you're a die hard Confederate who can't live in a non-Cofed ship but can't afford the Cruiser then this ship is for you. Some armor upgrades help, as do general engine upgrades. Selling the Rocket Launcher is recommended to free up space, and selling one of the two torpedo launchers won't hurt you too much and it will free up enough room to purchase 25 more torpedos.
Computer controled: The computer controls the Frigate better than any other ship. As soon as it becomes hostile it will unload all six torpedos followed by the missles. Close combat is risky since the Frigate sometimes, but not often, launches it's heavy rockets. However, an air strike from afar isn't recommended since it'll take you more than 10 missles to disable it. Fly-bys are the easiest way to neutralize a Frigate; fly by the it unloading all your guns and laumching a few missles or torpedos. Don't try to take a Frigate on in anything worse than a Kestrel. The Frigate makes a great offensive addition to your fleet.