I watched DS9 when it first came out and I was... underwhelmed.
But then I caught a few episodes in syndication, and it seemed pretty good -- the captain shaved his head; there was this guy (Gul Dukat?) who had really interesting conversations; there seemed to be action everywhere.
Is there a season where I can start without all of the boring stuff?
I rewatched it last year. Still good. First 1.5 seasons are rocky, but that's standard.
I finally convinced my friend to watch DS9 after he swore he never would, and he told me he thought it was the best Trek series once he finished it. IMO it was the crowning achievement of Trek and will never be topped. It has its stinkers but as a complete product, it was something special and is still way too under appreciated because it wasn't set on a ship with a registry ending in 1701.
I feel like DS9 is appreciated more when one was already introduced to the Trek world through TNG. The fact it came out during the peak of TNG was both a blessing and a curse. Curse because it could never outshine TNG but blessing because it was able to use the already existing world in a way TNG never could this giving people a whole new perspective for the aliens/politics of the Trek universe.
I almost feel like TNG and DS9 should be watched in tandem. Watch some TNG until getting a little bored of the mould then watch some DS9 until some of the episodes are getting a little dry then flip back. Taken together, they represent the best Star Trek has to offer imo. On a standalone, DS9 is better but it's also not Star Trek, which is also why it is underappreciated. When it first came out it presented itself more like all the other Star Trek spinoffs and some people didn't even realize it was actually Star Trek.