I am trying to navigate the comic mine field and wanted to get some opinions on what are the titles to avoid.
Depending on what you mean by "worst," my default answer is (as we've discussed) Avengers Arena. Quality-wise I hear it's decent though.
There seems to be unanimous agreement that Thunderbolts is terrible, and I've heard quite a bit of bad stuff about Red Lanterns, even from some people who still buy it.
I'd also dispute the Batgirl claim above. It's one of the few books I've consistently been enjoying.