The pros and cons would have a lot of variables. This is assuming only you have it, you can't get sick with anything very serious, you don't age at a normal pace, and that you would actually want to live forever.
Pros:
- Unlimited time for gaining knowledge and experience
- You get to watch the world progress in leaps and bounds
- You have more time to travel and explore
- You will eventually gain a deep understanding for people
Cons:
- You will constantly have to adapt and learn new skills
- You will have to watch all the people you grow old and pass on
- You have to financially plan to keep living in a more and more modern world
- You may get frustrated with watching the world make the same mistakes over and over again
- Your personality will likely develop to a point that others find it hard to relate to you
