Mostly GI side effects- nausea, abdominal upset, vomiting, gastroparesis. A lot can be mediated by carefully titrating but certainly some people cannot tolerate it.

Just met an elderly vet at the pool with a bad knees who said he's lost 50 pounds and his a1c went from 11 (really really bad diabetes) to 6.5 (pre-diabetes range) in the past year.

There will always be anecdotes of people who do poorly but study after study (and real world results) are showing convincing evidence that these drugs are making huge impacts on a variety of indications- diabetes, obesity, CKD, heart failure, cardiovascular risk reduction... continues to show results almost too good to be true.

In the real world 90% of people simply don't have the will power to sustain weight loss. It's not because they are bad or lazy... we're humans with money problems, stress, families etc. It is simply hard to maintain dietary discipline and a calorie deficit for long periods of time.