There was really only one season that I would skip over if given the option, season 6. The main complaint that tends to come up is that after 3 or 4 seasons, the writing seems stale because they had pretty much done everything already. One of the most interesting characters of the show doesn't show up until around season 5, so I'd at least go that far.
To me, the finest hour of the entire series happened in season 2, so I'd at least give that day a shot if I was in your shoes.