I finally managed to play the full Macedonian Aid today. I often had one card available, but was lucky today and had two almost from the beginning. The fleet isn't very useful, but the Macedonian infantry is superb - they hit hard and can take a lot of damage before dying. I was somewhat surprised that Philip's leadership rating is only 5, but his troops are so tough that it didn't seem to matter much.
The Macedonians helped me to storm a couple of cities and killed a bunch of Romans, but after only two turns the AI played a card that removed Philip's troops from the game. So while the Macedonians are certainly useful, you can't expect them to stay in Italy for long and give you support for many turns. I don't know how common that removal card is for the Romans, maybe I just had really bad luck when they played it so quickly. The Gauls are more reliable.
Wouldn't mind seeing some more Macedonians in the future. Maybe the next game is about Alexander the Great?
"But here we are in a chamber pot, about to be ****ted upon."
-French General Auguste Ducrot before the Battle of Sedan, September 1870