Reading this thread I tend to wonder why some people go places, they seem to want everywhere to be like home.
I think there is a definite mismatch between expectation and reality and people not really knowing enough about where they are going before they get there. And there's definitely something about what people like to do on holiday, especially whilst abroad.
I think you really do need to make sure you do your homework and work out where to go. Experience has taught me if you have only a few days somewhere, working out the very best places to go before you go really makes a huge difference to how you enjoy it.
One of the top grips on this thread is definitely the locals being rude - that smacks of just finding somewhere to eat whilst out, in a tourist trap. Knowing where to eat and which streets to avoid makes a world of difference. It definitely can ruin a holiday.
Rome is the one I can relate to most on this. I enjoyed going there - but we got ripped off by a taxi driver on a simple scam. Its the only place we've had that and it does leave a bad taste. It was also easy to see how it could be a massive disappointment - the restuarants we checked reviews for / had recommendations for were a whole world away from the ones we just rocked up to.
Its so worth realising taking a step backward to go to the next street over or walk a block or two more to the less touristy places makes a HUGE difference.
Or finding out what local events might be on.
The other interesting grip is the one about it being different on tv and how places with a sanitised makeover seem to be lowest in people's opinions. The US cities mentioned are particularly telling. As is Bali. Its the PR thing versus Reality. There's an instagram lesson to be learnt there.