Aristotle said:A couple of the people I've pitched this idea to have implied that such technology would never come about in a world with an active pantheon of gods and the availability of magic. In my opinion, magic doesn't prohibit science so much as it slows it's advance down.
I tend to disagree. What would most likely happen, IMHO, is that the areas of study in which magic is strongest would be dominated by magical research, and science would be concentrated in other areas. This is because science is all about building a systematic body of objectively determined knowledge, and magic precludes this.
Because of this, a realistic magic/tech mix would look nothing at all like our world, since some areas would be completely given over to magic. For example, taking a D&D style setting and advancing it to modern times, it seems likely that modern medicine would never really develop, since healing magic is so incredibly effective.
Another area to consider is social changes; a world in which there are one or more active pantheons of gods is going to be hugely different from any of the monotheistic religions that shaped much of our modern world. Laws, government, culture, wars, societal attitudes... these would all be different.
I just don't think that a recognizably modern world with magic added in is all that reasonable, unless the magic has arrived recently (a la Shadowrun). Of course, that doesn't mean it can't make a fun setting, just that it's the sort of setting where thinking too hard about how it got there is probably a bad idea.