I've actually gotten a few comments and e-mails about Paris not living up to certain expectations when visiting for the first time. This makes me sad to hear since I want everybody to see the same beautiful and fantastic Paris that I see. I guess that I could be partially responsible for this since I, most of the time, only show you the magical side of this city.
I think the expectations and hopes can be especially high for Paris since it's such an iconic city around the world. It's said to be the most romantic, the most beautiful and the city with some of the best food ever. When arriving with these thoughts in mind, of course it's easy to get disappointed if you don't see this right away.
Just as any other city the weather in Paris is not always what you would hope for. If you're really unlucky it could rain non stop during your Parisian getaway. But please don't let that stop you! Remember what some people say: "Paris is the most beautiful in the rain". Even though I don't agree with them the rain shouldn't stop you from seeing the city and doing what you've planned.
As for food... You should be quite careful in my opinion. The city doesn't just offer amazingly cooked classical French food and you can really find some horrible restaurants if you don't have the luck on your side. Do your homework before leaving to eliminate the chances of a disgusting meal. (And don't worry, the famous macarons are not to everybody's liking).
Depending on what you're used to the city can look quite dirty in some people's eyes. The Parisian métro is one of these things. In most cases this is not a pretty sight. Or smell for that matter. Don't expect Paris' magic to follow you under ground... If you're really unlucky you might just end up on the same train as a mini band with their trumpet, accordion and microphone on the highest volume.
One of the things that shocked me the most (when I'd been in Paris for a longer time) was how many homeless people there were in the city. Coming from Stockholm, I'm not that used to people sleeping out in the cold on almost every other street, smelly subways or how unbelievably many beggars there were. This was quite hard to get used to.
Perhaps you're imagining strolling down every Parisian avenue and boulevard, swinging your shopping bags around and stopping at every café for a croissant and a café au lait. Well, all streets aren't that strolling friendly all the time... Some days or at certain times you almost have to fight your way through a (tourist)crowd to get to the other side of the street.
... But the truth is that despite all these negative things (that you can find in every new city that you visit around the world) I truly love this place and I truly think it's just as good as I portray it to be. But that's just my opinion. Give the city some time and decide for yourself.