Peasants

[Evil Eddie]

Slav warriors are far better than peasants, they are a 100 man unit and cost the same to maintain. As soon as I am able to create these units I switch those provinces to spamming them out, allowing myself 2 units of them for each province I control. Have had quite reasonable success with them in fighting the Golden horde also.

I never make peasants as they just arent worth in, especially at the start of the game when you only have limited resources and may need every unit possible to fight. They flee far too quickly and die even quicker.

Dont even use peasants for suicide missions. A better unit for this is Highlander and/or Gallowglasses as they can usually inflict some damage, cheap to build and one of the cheapest to maintain. Great for castle sieges when you want someone expendable to assault a gatehouse.

[Knight Templar]

The only situation in which I'd train a peasent unit would be when I have about 200 florins in my cash and immediately need to improve loyalty in one of my provinces.
I had very bad experiences with them on battlefield; once my peasent 2-star general started to flee although his unit didn't take any casaulties.
I'd not even use them for suicide missions as it would bring me more harm then good. There are much better units for this (still cheap) like Ghazis, Arab inf, H. clansmen, Gallowglasses or Fanatics.

[matteus the inbred]

now that i've got VI installed i will usually use the slightly improved stuff like Thralls, Slav Warriors or Fyrd to govern most provinces if they're available...they're still dirt cheap, and they can fight much better. still gotta be peasants for the Muslims though.

can be frustrating waiting for a decent governor to spawn...i had a Hungarian campaign recently where i gave out none of my titles for nearly ten years due to a lack of decent governors, finally got one, and the very next turn he gained the Lazy vice...gah.