Darnit! I read through the whole thread intending to post the mañana joke, only to find that I've been beaten to the draw yet again!

BTW, I don't think buan-chara or anything like that gets the point, because as I understand it, "simpatico" describes an innate, immediate and unilateral characteristic of the person referred to, independent of who he/she might form friendships with. That's certainly the sense in which the equivalent French word "sympathique" is used.