We visited during the protests (July 3-6) but didn't actually see much unrest. Tourist areas are perfectly safe to explore — police are everywhere after 7-8 PM, and since it stays light until 11 PM, you won't have any problems.
Overview
My expectations were lowered by acquaintances who'd badmouthed the city, so the end result was that I was genuinely amazed. The tourist center is an absolute paradise. Every building is magnificent. Between the Eiffel Tower, the Arc de Triomphe, Montmartre, and the Louvre, there were maybe one or two buildings that bothered my eyes. They've preserved their history impeccably. They absolutely deserve respect for that.
Paris is probably the most ethnically diverse European city I've visited. The African and Middle Eastern population is very visible — more so than anywhere else I've been in Europe. In Germany, the Turkish community has largely assimilated over generations, especially the younger ones who've essentially grown up as German-Turkish hybrids. Here the dynamic felt different — there's a very large immigrant population that still feels distinctly separate from French culture. I honestly wasn't expecting Paris to be this multicultural. It was the single most surprising thing about the city for me.
I'd heard endless complaints about filth and urine smells. Anyone complaining about the dirt should come see our country first. The urine smell didn't bother me nearly as much as in comparable cities. Amsterdam, New York City, or any tourist center in Italy are far worse. Here it seemed more of a dog urine problem than human. The biggest issue was definitely the smoking — everyone smokes like crazy. If you sit outside at any venue, prepare for constant smoke from all directions. Worse than Turkey, I'd say. Trash seems to get collected around 9-10 PM, so if you're out on the streets around that time, don't be surprised by overnight garbage piles.
Food & Drink
The country is a gastronomy and wine paradise. We'd actually gone for wine education, and while I used to think they were a bit full of themselves, I was wrong. Their knowledge and expertise in this area is phenomenal. At any random cafe or restaurant, you can drink excellent wines by the glass for 4-5 euros. While Italian equivalents would be house wines made by the restaurants themselves, here they serve wines with AOC/AOP appellation certification in almost 99% of cases. And these appellation controls aren't limited to wine — you can see AOC/AOP labels on cheese and many other products.
Food-wise, we didn't get to try snails. The onion soups were decent (we'd had a much better one at a French restaurant in San Francisco). The duck legs were incredibly delicious, and the meats were good too. With a budget of 30-40 euros per person, you can enjoy very high-quality food-and-wine pairings. Even below that budget, the patisseries are absolutely phenomenal. The quiche at any random boulangerie patisserie you walk into will be superb. Our favorite quiche spot was Sylvain Marie near Montmartre. For restaurants, if you love truffle, definitely try Truffesfolies, and for a traditional French meal (duck legs), Le Sens Unique. Laduree felt a bit overhyped at first but is definitely worth trying.
What to See
The Sacre-Coeur Basilica and Montmartre area are absolutely beautiful. Climbing to the top of the basilica costs 7 euros and 290 steps. Quite tiring, but the panorama from the top is gorgeous — highly recommended.
Notre Dame was still closed for interior visits at the time, but worth seeing from outside. The fire photo exhibition set up in front of it is quite moving.
I used to think the Eiffel Tower was a bit overhyped too, but seeing it up close genuinely leaves you in awe. Maybe it's from years of exposure, but it looked absolutely beautiful. The fact that it was built in 1889 is almost impossible to believe. The only slight letdown is that it was constructed for an exposition — there's no deep history or story behind it. For the best Eiffel viewing spot, head to Trocadero Gardens.
Budget
If you're planning to properly explore museums and such, even 15 days wouldn't be enough for Paris. With its historic fabric, gastronomy, and everything else, it's a complete tourist paradise. After our visit, the fact that it's the world's most-visited city made a lot more sense. Definitely a destination I'll be planning to revisit.