In high school right now and my school requires either Latin or Greek. I'd say it's not bad. I mean as long as you're good at memorizing a few tables for declining and endings you're pretty much set. I don't get why people find it hard. It's interesting especially the culture parts. I'm noty really a language person but its not a bad class.

I'm taking Latin II right now and the idea people have of it being a 'dead language' is pretty inaccurate. Besides being very prevalent in many church ceremonies such as mass and in the Vatican City, Latin is the foundation for many commonly spoken languages, (i.e. the romance languages such as English, French, Italian, etc.) and can be very useful in increasing your day to day vocabulary. It's also a good idea to take Latin if you plan on taking any other foreign languages afterwards. And on top of that, you get to learn about the rather 'interesting' culture the Romans had. For example; did you know that the Romans all went to the bathroom together? Unless you had a chamber pot in your room, if you lived in Ancient Rome you went to a communal bathroom that probably looked like this. <-- See? Who doesn't want to know that?

Fun fact: English is Germanic yet over half of its words are Romantic and the vast majority are Greek or Latin roots

Yeah, I was in Italy for two weeks last summer, and it was interesting to see the linguistic similarities between Italian and French (and some of English), most of which I'm sure are due to Latin roots. The only reason I'm hesitant is that it means I probably wouldn't be able to get a summer job while taking this course.
I also hear the Romans used to bury alive vestal virgins who broke their vows. They are interesting, but damn those Romans did not mess around.

my question is : what for?
in my country we are obliged to study latin at the philology department, and we all hate it
if we studied mythology and things like that it would be cool, but all we do is grammar, so we all hate latin and we think it is the most useless object of all time
we would rather study any other language that can be useful for us in the future

I really enjoy studying languages; I'm currently majoring in French and studying German. The reason I'd like to take Latin is because in history classes of mine there will be excerpts with latin footnotes. You don't have to understand them to get the text, but the authors include them for citation purposes. It feels like they're talking over my head, snobby latin-speaking jerks.
So, yeah, I want to learn it out of pique.
But I'm thinking maybe I'll just take Russian instead.

i think that russian would be more useful to study, because i've heard that it is a language that is currently in high demand =D

Lingua arabica multe ultilus quam Russiarum est.
IMO, anyway. If you're in the US at least. Translators for ME langs are at a premium.