Currently, embryonic stem cells don't treat any diseases. Adult stem cells do. But, that doesn't mean that someday we won't have developed a treatment for something.
I'm all for stem cell research - both embryonic and adult. I don't have moral qualms about it. I'm not Catholic (or even really religious) and I don't believe life begins when sperm fertilizes egg. I guess it comes from having a baby. I realize that my living, breathing, walking, somewhat-talking child is about a million miles away from an 8 celled blastocyst living in a petri dish. Having gone through some rudimentary fertility treatment, I also understand that not every 8-celled blastocyst gets the opportunity to become a baby.
The mormons (latter day saints) believe in stem cell research since in their beliefs, life doesn't begin until the embryo has implanted in the uterus. I suppose this also means theoretically, they could believe in the morning after pill (Plan B) and other forms of emergency contraception. I could go off onto a rant about how these are not aboration pills, but I'll spare all 3 of my readers that (right now). The mormons seem pretty moderate on this issue. I even think most Americans want some research on embryonic stem cells.
And heck, if stem cell research is good enough for Alex P. Keaton and Superman, it's good enough for me.