Dear sidneythekidney,
You got a lot of good, solid advice from the other posters, but I'll just toss in my 2 cents.
I did quite a lot of research before finally deciding to donate. It is true that there are important methodological holes in the data. But note that there are very often holes in the data about lots of medical and surgical procedures; it's the nature of the beast. It does not indicate any conspiracy to entrap potential donors.
That said, I've sometimes been uneasy with "living donor boosterism" (not here on LDO) that makes light of the risks. So, you are asking the right questions, and deserve a straight answer.
In looking at the risks, "doubled risk" sounds worrying, but when it's from 1:100 to 2:100, it still seems "doable" to me (though the available numbers coming out of the then-new studies were somewhat more favorable when I first began my process 5 years ago than are some of today's newest numbers). Not that I look for risks, but I've taken bigger risks in my life already. And, while I was beginning my process, I kept telling myself: if I came across somebody trapped in a burning building, and I thought I could save them without killing myself, wouldn't I try? And, that's got to be higher risk than donating a kidney". Of course, as Sherri wisely noted, when it happens to you, it's 100%.
Still, there's one other point: you do have some control over your fate here. If you watch your weight, manage to keep your blood pressure down, and maintain an overall sensible life-style, you'll probably be improving your odds. Of course, this also relates to why transplant centers sometimes are so "snobbish" (picky) about giving medical approvals to donate. They try to screen out those at higher risk for later complications.
Be well, Snoopy