I like that other companies use BlueKai as well, so it makes it simple for them to share audiences. There is a number of useful, reliable 3rd party sources on BlueKai that we take advantage of often.
The user interface. It is very bad, does not make navigating around easy. Going from one audience to another and searching audiences is more of a process than it should be.
Also, the formulas for creating audiences does not allow for much besides the simple "AND" and "OR".
I also have been waiting about 3-4 days for an issue I submitted to BlueKai support and have yet to receive help.
See screenshot I attached to BlueKai having issues currently. This happens a lot.
We have a number of custom targeted audiences that we created in BlueKai and are used every day for campaigns. This allows for our advertisers to target almost always the audience they would like. With so many 3rd party data sources, we can reach higher impression counts.