I did my shoulder about 2 yrs ago, Grade 3 AC joint. I got referred to a specialist, Dr. Desmond Boker ( da shit when it comes to shoulders & elbows, apparently). I had to make the same decision, surgery or not. This is what he said to me: If I remember correctly, like, 80% of people who do their AC joint make a full recovery with no pain or restricted movement, Just a freaky looking shoulder. Of the people who have the surgery 10%-15% of them have continued pain &/or restricted movement. He recommended not to have surgery, go through rehab & see how it is with regards to pain & movement then decide on surgery. Alot of people will opt for the surgery cause they don't like how their shoulder looks. Also, you can have the surgery at anytime, say if your shoulder begins to bother you in 15yrs time, you can have the surgery then. Note that the surgery you have now & the surgery you have later on is 2 different types of surgery.
With regards to my shoulder, it's pretty good, I have full range of movement . On the odd occasion I get some aches & if I push things at certain angles eg, dips, fridge really hard my shoulder feels like it's going to explode but I think that's just a strengthing issue. Carrying heavy back pack can be uncomfortable as the strap presses down on the bone. Generally, I don't have any probs with my shoulder & if I did a bit of strength work on it I recon it'd be 100%.
One of my riding buddies also did his AC a little while back. He's shoulder was a little different. After recovery it'd just pop out on the rare occasion & he had some restricted movement & loss of strength (esp above his head). He recently had the surgery & going through rehab, it's too soon to know how it's going to be just yet.
Anyhow, this is just my personal experience, hope this helps.