I'm currently enrolled in Army ROTC but i'm a freshman so I don't have that much experience. But from what I've been through, I can honestly say that I love it.
Pros- its a great way to meet people, especially those who share the same passion as you. Also, its a good way to get involved at your college because there are so many clubs that you can join within ROTC. You stay in pretty good shape with PT, but you're still gonna have to hit the gym outside of ROTC. You get A LOT of respect, especially when people see you in uniform. One time a couple of cadets were out eating in a restaurant and a couple of people gave them $100 for the bill. Biggest pro: you can get a scholarship that pays full tuition, $600 a semester for books, and a monthly stipend starting at $300 which eventually becomes $500 by your senior year.
Cons- first off its Army, second, its ROTC so its a bunch of college kids, and not everyone takes it very seriously. I honestly hate when we are in formation supposed to stand at attention and everyone is goofing off and not showing any military bearing, but thats just my preference. Also, its really time consuming. For the first few weeks it was difficult waking up at 5 AM to run and then go to class later. But you will eventually get used to it.
Not too many cons. I say do it, if you don't like it, you can always drop it.