They are a mood killer, smell funky, and feel different. ---No there aren't any effects at all.
Mood killer? You are doing it wrong.
There is nothing wrong (but everything right) about going down on a man while at the same time opening up a rubber. Sure it takes talent, but I am sure the recipient will appreciate the practice. After donning the prophylactic, just hop on top and go for a ride. After it's finished, I like taking the condom off carefully as not to spill the delicious seeds inside, lick clean the deliciousness that is a spent penis, and pour the condom contents down my gullet. This might explain the extra pounds.