Indeed, the trading system is very complex and refined, thus interesting and rewarding. You'll never see the same items on traders, they all have chance to spawn rare stuff depending on the trader, it's quite randomized, of course they have their usual items which are spawned in stages ... not sure if that's the right choice of words, but the idea is you can't time items on traders and know exactly when they will spawn something good.
There are certain rare items, like some parts to make power armors which can be spawned like anywhere in limited amounts with a CD to re-spawn them again on a different trader in the wasteland.
Trading system is hands down, fully complete I'd say, improvements can be made, but it is simply very good already.
By the way guys, for some easy cash, experience check out the "DJ" quests on radio channel 0 and also permanent character bonuses.
You'll be asked for to be bring an item/s to NPC in certain city (npc will have ! mark near him so easy to recognize), always random and by bringing it you get rewards, sometimes the DJ says that the "client" will offer something special and then you receive character bonuses. So, one guy from our faction gave 24 rocks to some NPC and got +2 permanent carry weight, I got like +2% permanent electrical resistance and 11k just for tesla armor. These quests occur each 20 minutes from their announcement, each time something different, character bonuses depends on item if something special field medic first aid kit will be FA of course, energy weapon will be bonus to energy skill etc. etc. On top of that experience, once got 3k experience for 2 sharpened spears and 1.5k money, 7k exp and some 5k money for laser rifle with extended clip etc. etc. so can be extremely beneficial if your at the right place and time.
