I spent a good amount of money there recently and got peanuts out of it. I must have built 20 different campaigns to make something happen.
I move the same campaign over to TJ and Im almost instantly breaking even.
Where is the money on Exo?
Just you
TJ campaigns start out with better results, but since the sites you advertise convert similarly there is less room for optimization. 60%+ of your ad spend at the start of an Exoclick campaign may be thrown away but if you are patient and know how to optimize a campaign you can see higher ROI's on higher volume than TJ
I have noticed that ExoClick has a lot of shit but some gold placements can definitely be found. I have also noticed that ExoClick placements tend to be less saturated then TJ and that the campaigns run longer.
Although I still think that the real big ROI's are found on not-so-popular traffic sources. Which I'm still searching for...
What bowlcutah and johnny said. 
I've outlined a viable exoclick strategy in this post:
http://stmforum.com/forum/showthread...l=1#post200678
The rest of the thread is littered with more valuable insight as well. 
Amy