No one seems to be answering this.  All I can point to is what is available
at different web sites.  I think incontinence is listed at about 1%.
Impotence at 4%
http://adam.about.com/reports/000071_10.htm

It seems to me that  retro ejaculation is quite common but may be temporary.

Gerry, before you go TURP I suggest you check out PVP.  I had it done
and am very happy with the results.

I have had 2 TURPS. One in my mid to late 40s and one in my mid 50s. I
did not suffer from either potential side effect.
Steve

I had a TURP back in September (I was 57).  The results were good after a
few weeks and got even better after a few months. It was the best thing I
ever had done.  Never had incontinence or impotence.  Sometimes I won't
urinate for six hours and then when I do go it comes out like a fire hose.
Before the TURP, I would go at least every hour, day or night.  My doctor
had a lot of experience.  I know that all TURPs don't go as well, but I was
very happy with mine.  Funny thing, but my prostatitis is essentially gone.
I had prostatits since my middle 30s.

Phil