My first time, I wasn't sure I was prepared to take a load in my mouth, but as I became engrossed in actually sucking his cock, I realized I wanted him to cum in my mouth and, what's more, I wanted to swallow it. When he did come, only the head of his cock was in my mouth, so I immediately felt his warm sticky goo on my tongue. I was in ecstasy. I continued to suck him for a bit, then I swallowed and finished up by licking up what had leaked out on to his cock and balls. It was definitely salty/sweet, and delicious. I don't think I've ever detected the ammonia smell, but my sense of smell is somewhat lacking.
I realized at the time that I would never again experience taking a load in my mouth for the first time, and that left me feeling a bit sad. I soon learned that it didn't matter - every load is perfect, every load is sacred, every load is swallowed. If I get fucked by a guy wearing a condom, I ask for the condom afterwards and suck his load out of the condom. I then clean off his cock.