Immortality - Gift or Curse?

Alright so I have a little obsession for immortality, meaning you do not die, which I personally think would be great but first for this thread lets say the following occurs when immortal.

1. You never age.
Example: Become immortal at 23, stay 23 forever.

2. Your body never gets older than your age.
Example: Your 23 and look 23 for ever, you don't get grey hair etc.

3. You are immune from viruses, and diseases.
Example: You don't die of radiation, or cancer nor do you get any illness

4. There is a way to die but it's not known you must discover it.
Example: You need to research thousands of years of documents to figure it out.

My Opinion - Detailed.
This is my opinion, I'm sure people will disagree but it's only my opinion and I respect all others opinions!

Personally Immortality is a good thing, a gift in my opinion as you have the chance to live forever and be able to build your knowledge so that you know the past and present in detail.
You could become an expert in every area and have time to learn more.
A downside being that you would see friends and family die around you but over time you would get over it.
Also say the Government find out you are immortal, they would want to do tests and shit which I would not like to happen to me.
I could go on but that's just some of the things that are semi-important.

What is your views on immortality? Is it a good thing or bad? a gift or a curse?