I've had it and when it first occurred, it was very painful, frightening, and embarrassing.
I had no idea why my balls were so swollen and painful. Sometimes I was in so much pain that I begged my partner to cut my left testicle off!
Due to embarrassment, I put off treatment for a lot longer than I should have.
Now that I know what it is and how I got it, I do have occassional reoccurrences, but as others have stated, antibiotics will clear it up.
Basically it is a bacterial infection that mainly occurs due to unprotected anal sex.
We all have harmless bacteria in the colon that aid in digestion. Unfortunately, that same bacteria becomes harmful when, during anal sex, it is displaced and transported through the penis and infects the testicles.
I remember that my first occurrence was during a period of time where I was really into anal sex. I really got addicted to fucking guys without a condom and I paid the price with epididymitis.