when i first developed my lated allergy we tried to use these - they transfer heat much better than latex and are a bit larger than the Trojan non-latex condoms. the female condoms are made of the same material and are (obviously) much larger but considering that he did not like the female condoms and the durex ones were too small, we decided to do with out - but i wanted to second the goodness of non-latex condoms!
As far as them protecting from STI/STD's honestly - we use the same material for gloves in our lab and handle human biological materials all day without worry, so i really don;t think that there is much to worry about in that respect.