I was slogging before Glenn started getting less screen time, and I didn't like the Savior arc and was not particularly pleased that it just went on and on. I was completely unconvinced by certain romantic pairings as well (Carol and Ezekiel? really? and they are not the only one).
I really loathe the Whisperer arc and wish it would just stop. The only thing keeping me going is a touch of OCD-like devotion to completeness: If I am in on a show at the start, I will watch to the end even if I start to hate it.
Fortunately, this mentality was not an issue with Heroes; I started watching it on DVD a few seasons in, so I felt no obligation to continue when it started getting REALLY bad.