I use IB and recommend it. I also participate in their forum.
But you made a good point about the tool bar and the novelty of the sites displayed. Yes, you are essentially marketing to other "marketers" and "sellers" - so 2-tier programs are best for that crowd if you can get them to sign up under you without going around you. If you are a program owner, that's a good place to hang out.
IB also seems to have a mix of "newbies" and a few "veterans" in their forum. I have enjoyed good, useful traffic from them.
IB's "by invitation only" concept is strong because I'm sure Mark and his team knew that people would simply try to bypass the little popup window and go straight to the source to sign up. Why people do this beats me! When I sign up under someone else, I use that to get them to sign up under me for yet something else. It can turn out to be a win-win.
Now you do not have to sign up for this, but for illustration's sake, I developed a special invitation at
http://themoneyreport.net/ib.html - Notice that it's different than just the little IB window that everyone else is using. You will see a variation of this too at
http://themoneyreport.net/ -- (I.E. Only.)
Notice that if they don't sign up for IB with my invitation, they may sign up for another $.10 cents a click program that I promote as well and they also hear an audio about my main site. If you like what I am doing with IB, perhaps you could use this idea to recruit people for your own programs.
IB has another feature that some will just swear when they find out about it and others will swear by it: MailSpaceTM Ads...
MailSpaceTM Ads sends a members ad and your IB link out with each email that goes out from your PC! I can see people cringing on this one. But the idea itself is ingenius.
Another thing I have noticed is how their forum is growing. The software used on the Forum is a bit cumbersome and you have to manually create your sigs with each post...
Overall, I like IB and I don't see any harm in using it. It's another great marketing tool and idea.