*No spoilers, TLDR at bottom*
When I first learned about Saiki K, I was hesitant to give it a shot, but after getting it recommended to me time after time, I decided to try an episode out at the very least, and I'm so glad I did. It's quite difficult to write an objective review on this show because comedy is subjective, and I can't say that this show will be enjoyable for everybody to watch because not everybody likes the same type of humor. But, if you enjoy deadpan and gag humor, this show will definitely appease you.
The best thing about this show is the 5 minute episodes - you never feel bored (if you like the jokes), and Saiki K never drags its feet to getting to the punchline. The fast paced and high energy episodes ensure that each episode is never dull, and there is a different scenario going on every episode. The jokes keep hitting you every 10 seconds as you watch this show, which I think is beneficial for Saiki. Too many comedy shows take an entire episode to lead up to one big punchline, which is still good, but Saiki K's rapid-fire episodes that are filled to the brim with humor is a refreshing change.
Aside from the episode structure and the humor itself, the cast of characters in Saiki K is surprisingly large and diverse. There's probably more than 20 recurring characters, and unlike some shows, they are all very clearly distinct in terms of how they are drawn and their character traits. You have the vain yet beautiful Teruhashi, the dumb and ugly beyond logic Nendou, the weird chuunibyou Kaidou, the former delinquent turned regular student Kuboyasu, the overly enthusiastic and athletic class rep Hairo, and the pervy psychic and esper Toritsuka. And that's not including Saiki's family and the many many other distinct characters. Each episode is a blast because of these unique characters.
Overall, I loved this hilarious show, but would I recommend it? I would recommend anyone who even remotely likes comedy to watch at least one 5 minute episode before passing judgement. And if you do like deadpan humor filled with exaggerated characters in extremely fast paced episodes, this show is perfect for you.
TLDR; If you like comedy a little bit, watch at least one episode.