Hi Leah,
I donated 3 years ago last October. I was 39 at the time - I am 42 now. In my case, I feel just as well as I did before the surgery. I go in once a year to get a checkup and get my kidney function checked, and to date, I am healthy and doing very well. For the first 2 years, my creatinine stayed at 1.1 and since I hit the 2 year post donation mark, it has come down to and stayed at 1.0 now.
The only lifestyle changes I had to make are that I can no longer take ibuprofen. Other than that, I eat the same, drink the same, exercise the same, my Husband and I like to travel as much as possible. I do nothing else differently now than I did before the surgery. (Actually, I think I excercise a bit MORE since the surgery). I have always been told I am kind of a hyper/high energy person, and I am still told that. LOL
You are correct that in some cases, people do have issues. Each person's situation is unique, but I wanted to share my experience with you. In my case, I absolutely, without question, would do it all over again. I have no regrets.
I wish you all the best and please let us know how you are doing. Please ask as many questions as you like. There are many wonderful people here on this willing to listen and offer advice/share their experience.
Linda