Don't know where you heard that from. I found weapons pretty much in the same staggering as vanilla. There are just types of them! There are also more 'upgraded weapons' which is a nice touch. As for ammo, again, as vanilla. I haven't run out once though I have had to switch weapon type quiet a bit when one type of round gets a bit low.
As for diffilculty, it's smarter but not much harder. If anything, enemies don't spot you half-way across the map a they used to do! Also, you can create teams! Befriend a stalker and you can ask him to follow you. You can even outfit him. Plus, veteran stalkers can actually survive longer than 5 minutes now. There's one I bump into occaisionally who's saved my life a few times!
As for money, you do get less from traders as you say. However, there are more types of artifact to find and trade which are worth huge sums. This makes stalker a game about finding rarities as originally intended. Not a game of who can carry the most guns. I think it's great that I no longer feel obliged to crawl everywhere dragging a sack of rusty soviet equipment to sell.