It does seem like the consensus is that this is less likely to be efficient in preventing STDs. Perhaps as an alternative for couples that tend to be monogamous, the fear of STDs wouldn't be as much of a concern but then if that were the case, why use anything? I'm thinking that the reason this hasn't taken off and was not supported by the Gates Foundation (funding), was because in other countries, such as 3rd world countries, the potential for increased SDT transmission might be a big issue.
I agree that it does seem like it would be messy depending on how full the 'reservoir' gets. I also agree that 'gluing' something to the glans makes me wonder how the body would react. Supposedly you can even shower with it on so that means the glue must be pretty strong. I'm thinking irritation, rash, sore, not the things I want to experience on the end of my penis!