Rear heat: Goooood
Front heat: Not so much.
I saw a related thread that I think may have addressed this, but being something of a tech tard, I'm not sure exactly what they were talking about.
I have a 99 Expedition with the 4.6 Triton and while the fans blow hot air out of the rear vents, I get nothing but cold out of the front. Heating the cabin is possible with just the rear, but now that the cold weather is setting in, I've discovered that I can't effectively defrost or heat the feet.

 

Either the heater core is blocked or your blend door is broken. If you feel the 2 heater hoses going through the firewall to the front heater core are they equally hot or is one much cooler than the other?

 

Oh....ummmm.....I'm not sure where those are. Can I reach those from the engine compartment? And is it obvious which is the front and which is the rear?

 

Yes and yes.