I have used traffic exchanges for several years with varying degrees of success. Results vary greatly depending on what you are promoting and which exchanges you are using.
The larger exchanges get a lot of new members regularly, so there are always fresh eyes on your pages. On the down side, they will have many thousands of pages in the rotation. It is easy to get lost in the shuffle.
Smaller exchanges do not get as much traffic, but they seem to be more responsive at times.
My best advice is to try several, track and test, drop the ones that are not performing and then try some others.
Just be aware, there are a lot of hyped promotions out there as well as plenty of outright scams. Also, you will find a lot of "tire kickers" on these sites. Many of these people will never actually do anything. They are looking for the "something for nothing" programs.
Even these people will eventually either quit or realize that such a program does not exist, despite all the hype. If you have your auto responder working for you, some may eventually come around once they learn the truth.
Traffic exchanges are time consuming, unless you want to spend money on them, so be sure it is worth your time before you jump in. I advise people to test them first, before spending money on credits that may not yield results.