You have already read threads, if not more, asking such a question, why are you asking this? What, you have to read the same answers several times before it sinks in?
It hasn't ever worked greatly for me, however i have only bought bulk traffic which has more than likely been from junk traffic exchange websites or something similar. I have always had better conversions from search engines, adwords, paid links/banners and direct traffic.
Don't waste your money. You're better off paying for Adwords, if you're going to spend money on actual targeted traffic. You could look into linkreferral.com or similar.
I bought traffic before, but i can tel you that buying traffic is wasting your money. All those traffic bring nothing for you. It is better to get some natural traffic. Or buy banner space on high traffic site which provide better result
When you buy traffic all you get are fake clicks. It is a complete waste of money. You might as well just drive around town with your window down and shout out your website name to all passesby. You will get better results than with buying traffic. Shoot - here's an even better idea - hire some of your local homeless folks for like $10 or so and they will show a sign with your website name instead of the usual "Hungry and need help." You may even get some publicity out of it with the local media if you pull it off right.