Per the Advocates For Youth: Condom Effectiveness Condoms are basically around 99% effective when used properly. The problem is, people aren't always perfect, so the real condom effectiveness rate is somewhere between 80-95 percent. If a condom does tear or break during sex, you should quit immediately and go to a health professional.
What Bryan said: Around 80-90%, higher if used properly (which includes using the right kind of lube!)
I realize not to use oil based lubes like Vaseline. I am wondering though, what can be similar in slickness? And I appreciate the info, guys.
I prefer silicone based lube myself. It doesn't hardly ever get sticky, it's still condom safe, and it doesn't wash away if you are playing in the shower. The only down side is that, that last part makes it a bit more difficult to clean up.