I almost always mount a missile on my fighters. Even if you don't know how to use them, it's good for keeping the enemy's head down. Most people freak out a little when they hear "incoming missile" and sometimes that's all you need. With enough explosives, you'll disarm your opponent and he'll be forced to shamefully retreat, and leave you laughing at his total pwnage.
Probably the best thing going for missile use is that people either use too many, or none at all. With just one or two mounted, you can be an unpredictable foe-- unpredictability being the key to dogfighting.