My group decided to set some guidelines for running compels like "On Fire" or "Stunned" (that is, with boring aspects, really). Maybe they'll help your group too:
Compels should, ideally, narrow the character's choices rather than force them to a specific action. They should be used for narrative effect and tactical benefit (if via an invoke for effect) and not for mechanical benefit (that's what the +2s are for).
Compels can do save or suck type effects with the caveat that they only last for a single exchange. That is, if the target is "Stunned" I can compel this to prevent their acting for a single exchange. If the aspect is sticky, I can continue to compel for as many fate points as I'm willing to give him, or until he removes the aspect.
Compels on aspects like "On Fire" can be used to initiate an attack, but ideally the character would be given a choice. (Ex. Here's a fate chip. You're on fire. You can either stop, drop, and roll this exchange to avoid burning or burn.) The strength of the attack would equal the strength of whatever established the aspect (if no roll established the aspect, unlikely in this case, the GM sets a reasonable strength). Characters defend with the appropriate skill (in this case, athletics).
Again, these are not RAW but extrapolated from RAW and playtesting it different ways. Take what works, ignore the rest.