I find that I can only watch up to "Lost & Bound". I can't stand seeing Cole's descent into the Source storyline, Phoebe's abandoning him (despite her devotion to him just one season earlier), and his " gone insane because I can't die" plotline. The character certainly deserved better.
I tend to skip most eps of season 5 (with a few exceptions like Y Tu Mummy Tambien and Sense & Sensibility). Season 6 I choose to watch Chris Crossed if only to get to see Future Wyatt and his interactions with Chris.
Season 7 I also tend to skip with the exception of Imaginary Fiends (to get a bit more on a good Future Wyatt), and Show Ghouls (sure Billy Zane is a bit of a ham, but a likeable one. Although I can see this ep easily having originally being written with Cole and Phoebe in mind not Drake).
Season 8 I tend to ignore until the finale.