Good or bad for what? What interests are we concerned with promoting here?
If your main interest is in converting people to atheism, then militant atheists are probably a good thing. You won’t get far with winning converts unless you are prepared to make a fuss about how and why atheism is a good thing.
Personally, however (and I suspect I share this view with a majority of other atheists), I do not care too much about spreading atheism. Most religious belief, in itself, is fairly harmless. Yes, religion can be harmful when it gets harnessed to other prejudices, such as homophobia, but the connection between religion and homophobia (etc.) is largely contingent. It is perfectly possible to be a devout Christian (or, I think, Muslim etc.), and gay, or gay friendly, and many people are. Likewise it is perfectly possible to be an atheist and a homophobe (or misogynist, or whatever). If you convert a homophobic Christian to atheism, there is no guarantee he will not still be a homophobe.
If, on the other hand, your main concern is furthering the advance of science and rational thought, and public support and understanding of science and rational thought, then I think militant atheism often does a lot more harm than good. If you go around telling religious people, even not particularly devout religious people, that science proves that there is no God (which is not true anyway) or that religious belief is silly and irrational, then, in most cases, they are likely to become more intransigent in their religious beliefs, and, what is much worse, convinced (as they may not have been before) that their religious commitments mean that they must reject science (or important pats of it, notably evolution) and rationality in general.
Historically, with occasional rare exceptions,* Christianity and science have got along just fine. Indeed, ever since Christianity became the dominant religion of the West, until very recently, almost all scientists have been Christians, often quite devout ones, and the research of many of the greatest scientists of history was often largely motived by their religious beliefs. Likewise, the official theology of most of the major Christian denominations, even today, is fully accepting of modern science, including such things as the Big Bang and Evolution by Natural Selection, and teaches that science is not at all in conflict with Christian faith. The notion that everything in the Bible (and particularly the Genesis creation story) must be understood as literally true was refuted by St Augustine, probably the most influential of all Christian thinkers (apart from Jesus himself, and the Bible’s actual authors), in the 5th century AD. It is true that there are, indeed, growing numbers of militant fundamentalist Christians who believe otherwise, but they constitute an aberration from the mainstream Christian tradition, which has always valued rationality (except, perhaps, when it comes to a handful of key items of dogma, such as the Resurrection and the Trinity).
If you want to promote the interests of science in a country, like the United States, where the influence of Christianity is strong, you will do much better to make people aware of the above facts, and thus reassure them that they can safely believe in both Jesus and evolution (and science and rationality in general), than if you tell them (what is in any case false) that Christianity and science are incompatible with one another. When militant atheists promote this message, they are, in fact, contributing to driving people who might otherwise be science friendly Christians, into the arms of the science-hostile fundamentalists. It is no coincidence that the rise of Christian fundamentalism (as opposed to Christianity) is almost entirely a 20th century (and, originally, almost entirely American) phenomenon. It was the scientific triumphalism (and the associated implicit, sometimes explicit, atheism) of early 20th century America (see, for instance, the works of J.B. Watson) that drove many American Christians away from science and towards militantly anti-scientific fundamentalism. That process is still going on, and fundamentalism has moved from being an insignificant, fringe movement to a large and powerful one that constitutes a real threat to science, science education, and even good governance and the stability of the world’s economy!
Frankly, the militant, in-your-face brand of atheism (which has been around a lot longer than Richard Dawkins and his ilk) is partly to blame for provoking this reaction.
*By far the best known and important exception is Galileo’s conflict with, and eventual condemnation by, the Catholic Church. However, the widespread belief that this was evidence of a deep ideological conflict between Christianity (or even Catholicism in its 17th century form) and modern science, or the notion of a heliocentric universe, is almost completely mythological. Galileo, who always considered himself a good, loyal, believing Catholic, was caught up in the power politics of his time, and the claim that his teachings about the solar system conflicted with an (obscure and ambiguous, and doctrinally insignificant) passage in the Bible almost certainly functioned as an *excuse* to censure him rather than being the real motivation behind his downfall.