I've watched the vast majority of the episodes, but there are some I just can't bring myself to watch. Judging from the plot descriptions, there are a few episodes that contain sitcom tropes that I absolutely hate - like "Mary gets someone fired and feels bad for them, so she gets them a job at her office" and "Mary dates a guy whose kid is a total brat."
Having watched most of the episodes, I think the show's characters are straight-up iconic, with the exceptions of Murray and Phyllis.
Murray is just boring as sin. Episodes about him were filler. His main purpose was to deliver "zingers," but I hated most of his zingers. He even managed to suck the humor out of Sue Ann! The only times I didn't enjoy her were the formulaic "Murray makes a slut joke then Sue Ann makes a bald joke" exchanges between the two.
With Phyllis, I think the writers were very inconsistent. Sometimes her phoniness and pushiness were presented as being kind of adorable, and other times she was just a vile human being. (Like when she harassed Mary and Bess about that stupid essay, or when Mary and Rhoda figured out that she and Lars secretly managed the building without doing any work). I've never seen her spinoff, but I hope they made the character tolerable - which she often wasn't on MTM
I have mixed feelings about Ted. He certainly gave us a lot of funny moments, and Ted Knight was great at playing him. But I think we saw way, way too much of him. There were too many Ted episodes. I'm sure he was an easy character to write for, because his personality was so over-the-top, and he had so many ridiculous characteristics to draw humor from. But seeing so much of him made him really, really hard to take.
I will say, though, that I appreciated the episodes that gave him some depth (like when he was dejected about his sperm count, and when he resisted the urge to cheat on Georgette).