My first, gut reaction when I read your question was that the guy was insecure. He was nervous about your affection, uncertain about his own sexual prowess, and -- in some weird way -- fishing for reassurance from you that you find him attractive and aren't hung up on your ex (or overly concerned about a man's level of expertise). ..
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I think the way you handled it was just fine; you stayed true to yourself but deflected his request gently. After all, he's on a need-to-know basis at this point. If at some point in the relationship, if it continues, you feel like divulging some more, that's fine; but it's also A-OK if you keep the details of your previous sex lives a secret. That's your prerogative...

Some people are more private than others, some people like to get all the nitty gritty details ... the question you have to ask is why does he want to know?..
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Is it so he'll be "better informed" in knowing ur likes/dislikes?..
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I could understand if you wouldn't want to say ... "He was the most incredible fantastic lover, ya know, knocked my socks off every time...We liked doggy-style and reverse missionary mostly which worked out well I was going to wait to tell u this...But, apparently, I make this really funny face when I cum and he told me that it would crack him up and throw him off ... anyway I digress ... where was I oh ya ... bj were also big ... he loved getting them and I loved giving them ... I have some pictures, wanna see?"..
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That might be a bit much but what's wrong with talking about your past, it gives good insight into the future...
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Angie..

My boyfriend and I have discussed non-specific things about our past sex life, but we didn't discuss this type of stuff until we had been intimate for a while. If he was to ask me on our first few dates about my previous sex life, my first idea in my head was that he's trying to either figure out what kind of action he was in for (which would show me he wasnt looking for commitment) could get or figuring out if I was a slut or not. This definitely isn't a typical 'getting to know eachother' question. More of a personal one that you may or may not answer later on if a relationship is established...

I bet you ask one of those ettiquette ladies, this line of questioning has never been and will never be OK. But times have changed and some people seem to think such questioning is fine. I think your reaction was good, and if he pursues it any more, just tell him he's making you uncomfortable. If he still persists, then he doesn't care about your comfort...

Have you already slept with the new guy?..
And what exactly was he asking? I mean, have you been tested for any diseases I might catch is a reasonable question. ..
I had an ex who had a very interesting sex life before meeting me. And some of it was just really good story telling. And he was a dirty talker anyway. So, it was just interesting to hear. But otherwise, I haven't really discussed a lot of sex with other people...