Traffic Exchanges are good for getting leads but not necessarily for direct signups for your affiliate programs.
The reason being that most people don't join them looking for programs to signup for, they join them to advertise their own opportunities, the ones they are already in.
So people who are "surfing" aren't looking at your opp, they are just cruising through.

For example, I joined the Moneylegs four programs to send 2000 hits to my SIM gateway and tracked the results. They all arrived - 500 hits from each program - but not one signup. And that was with the opportunity to get some free stuff!

However I joined some other lead generation programs such as LSN and ListGenesis - primarily because they are listbuilders - and advertised them on Moneylegs. I got signups immediately.
The reason for this is that people who are surfing and not getting results are open to look at new recruiting programs

I can now send my affiliate programs - including SFI - to my opt in list.
Also keep in mind people who might not signup for SFI as a business from FREE may try the SIM pack and try SFI as a second income opp, or they may join the IAHBE to help their current business. Or they may want a book such as Mining Gold. Once you have a list who will listen to your suggestions and trust you, especially if you helped them build their TE/List programs, they will be more open to buy from you. It's just down to how you work it.

For example, imagine you join a traffic exchange such as Traffic Swarm, MDT, WebMaster Quest or whaterver and you are doing your 100 sites an evening regular surfing (which most people do to generate leads).
You see ads for other programs such as FSC, DHS, XSTore, etc.
What do you think of these?
Do you drop SFI and sign up to that program?
Do you think it's something you may join up as a second opp to SFI?
Do you see them as just "other" biz opps?
Do you stop for a look or just carry on surfing?

Now, after a few weeks of surfing for credits and getting no SFI signups you start to notice listbuilding tools, LSN with it's "cool lead capture pages", Moneylegs with it's dancing characters and music (currently using speech "the home of the 200,000,000 offline ad campaign join free today").
What do you think of these?
Do you think "I could use that to sign people up"?
I could use that tool to build my contact list?
If this has caught my attention, maybe it will catch other people's attention and they will join under me?

Obviously these are questions only you can answer. It depends on whether you already surf TEs and what your experiences are.
My own answer is that I sign very few people to my affiliate programs from the TE's but when I joined the other, downline building and listbuilding, programs such as LSN and Moneylegs, and advertised them, I started getting signups, started building a list, and now get credits on all the TEs from my referrals doing their own surfing.

Now I use surfing to build referrals in the TE programs and build a contact list.

I build relationships first.

Remember:

In Network Marketing, the NETWORKING always comes before the MARKETING.