Without reading all of the replies before writing this, I suspect that 90% of the responses will fall into one or more of the following categories:

1. Yes, underpowered. Friends don't let friends carry mouseguns.
2. No, with modern ammo you will be fine because shot placement trumps everything.
3. For all those who said it was underpowered, at least one person will say some variation of, "I bet you would not want to get shot with a .380."
4. Someone will trot out the tired old phrase that "more people have been killed with the .380 than with all the bigger calibers combined." I used to hear this about the .25, back when .25s were still in the game.
5. A .380 carried with you is better than a .45 in the trunk. This person may quote Skeeter Skelton, who liked his PPK, but only if old enough to remember Skelton.
6. With "super bat hi-vel zombie killer bullet made of exploding unobtainium," the .380 is now the best stopper in the world.
7. The .380 may kill lots of people, but killing is irrelevant. The .380 will not stop anyone fast enough.
8. Your ordinary thug will run away at the sight of any gun, so .380s are fine.
9. The following interchange was heard the last time two people argued about the .380: "James Bond used a Walther PPK - that was a .380, wasn't it?" "No, Ethel, Bond used a PP in .32, at least in Dr. No." "Well, then, if a .32 is good enough for 007, then a .380 is a real manstopper." "You do realize that Bond is a fictional character created by Ian Fleming, who first armed his character with a .25 caliber Beretta, don't you?" "See, I told you. If a .25 is good enough for 007, then certainly a .380 will get the job done." "I give up."
And, the 10th thing you are likely to see in this thread: Carry the .380 because anything bigger will not fit in your pocket.