well are they worth taking? if so, why? a friend is selling 15 of ´em and im considering buying them, just that I really need to find a use for them. otherwise it´s money better spent elsewhere. so, are they worth having in a bestman army? :)

Sometimes. But in my opinion they work best at supporting minotaurs or something not being the key unit. The only real use I have for them is a unit of 12, generally naked which supports other units.

As they are armed with Great weapons, they can do some serious damage to High Toughness Characters like Ogres and Tree Spirits and such. I find them very useful indeed in my armies.
Pestigors I think have it the best, as Fear can be a game breaker, but regular Bestigors work just fine.
I say take them, as they will provide some solid support in the form of a Core choice.

Stratos

I shall see how I will do, if they become like this main unit 20 strong or as shaargor said, a supporting unit.. or if I take them at all ^_^ they are pretty expensive.

I'd say yes they are worth taking. Their strength 6 great weapons coupled with their high movement (meaning that they're likely to get the charge) allows them to do some serious damage to just about any other infantry unit and with a decent combat character in the front rank they can become quite deadly.