I have heard about and wanted to watch this for a while but only got access to it this month. I haven't watched Season 4 yet but wanted to write about the seasons I have seen.
Seasons 1 and 2 lived up to everything wonderful I have heard about them and more - probably the most original program I have seen in years. The plotting and style and cast were a delight. The team of Steve Martin, Martin Short and Selena Gomez seemed unlikely but they were terrific together. All things that you can find being said all over the internet.
However I was disappointed in Season 3. It's not terrible by any means but there was something "less" about it. I think one problem is that there is less intricacy to the plot, it's more in your face. Also the kind of detail and empathy shown to all the characters in the first two seasons are missing - the hidden depths and complexity that made them feel real and personal isn't there and we're left with types rather than individuals. They're fun and entertaining but we don't really care about them. Meryl Streep and Paul Rudd are talented actors and I like them both but here they're just plot pieces and don't feel real. (Ms Streep has a decent first scene where she auditions but that's really the only chance she's given to do something real with her character.). They don't really have a chance. I don't know if this is the fault of the script or the direction or both. The three leads fare better but to a degree they're coasting on the good will they built up in the first two series and I wonder why they kept the them separate for so much of the time. It's watching them together that's the fun.
I'd like to give a mention to James Caverly who plays Theo. He's an excellent actor. He's mainly in Season 1 but when he's on screen he's subtle and convincing.