"Islamism" is not a helpful invention. Apostates from Islam, Wafa Sultan and Ayaan Hirsi Ali and Ibn Warraq, treat it dismissively. It represents an attempt to somehow appeal to Muslims -- that is, to those who are thought of as "moderate" possibly because they remain largely ignorant of the texts of Islam, or because they simply try to put those texts and teachings out of their heads. In a world where all we had to worry about were Muslims, because Infidels understood thoroughly the nature of Islam, its meaning and menace, then perhaps -- just perhaps -- a word such as "Islamism" might be acceptable.
In the real world, however, most non-Muslims have no real idea what Islam's texts contain, or the nature of its commandments and prohibitions, or the inculcated view that there is a state of permanent war (though not always open warfare) between Believers and Infidels, and that it is the duty of Believers to work, sometimes as a collective, sometimes individually, using whatever instruments are available and effective, to remove all obstacles to the spread and then to the dominance of Islam. In that world, that is, the real world in which we now live, use of the term "Islamism" is unhelpful. It can even, as it sows further confusion, be downright dangerous.
I even fail to see any evidence, whatever the damage it does to Infidel understanding, of any help it provides to Muslims who wish to reject what Islam, as a politics and as a geopolitics (for Islam is a Total Belief-System, not merely a collection of rituals of worship) insists upon.
Indeed, if one not only must keep in mind, as the first priority, the right education of Infidels, and if one wishes for them not only to understand the texts, tenets, attitudes, atmospherics of Islam, but also to be able to connect the political, economic, social, moral, and intellectual failures of Muslim states and societies and even families with Islam itself, a mitigating concept such as "Islamism" stands in the way. It makes things more difficult by obstructing a clear view.
The distinction between "Islam" and "Islamism" which some find acceptably machiavellian is, I think, more akin to a boomerang. Its proponents posit something called "Islam" which has been stripped of its politics and geopolitics, and left only with the rituals of worship. Then they take that politics and geopolitics and the instruments used to further them, and put that under a separate rubric of an invented thing called "Islamism." They do this because we are all either to believe, or to pretend to believe (I don't know which is worse) that we, non-Muslims, can do this -- that we can split Islam in two for calculated purposes, so that we might smuggle in the real theme, that Islam itself is the problem, in the guise of opposing only Islamism. This simply confuses, and in confusing, disheartens.
Imagine a United States where 300 million non-Muslims, or at least the adult part of that population, was worried about "Islamism," but at the same time was not at all worried about good old "Islam."
Well, would that outcome, presumably favored by those who push this Islam/Islamism distinction, worry you, or not worry you?
If the proponents of this distinction would kindly list the passages in the Qur'an and Hadith that "Islamists" rely on, and tell us how such passages, and such reliance on them, differs from what those who believe not in "Islamism" but "Islam" take as their texts, we will all be happy to accept their superior knowledge and understanding -- a knowledge and an understanding that presumably goes far beyond that of the great Western scholars of Islam, every single one of them in the days before the profession itself became islamized and peopled by apologists. Some of them now are no more than direct or indirect hirelings of the Arabs, such as Esposito, and others who "found the answer" to their own spiritual search in Islam, and still others who, careful careerists, are afraid to offend the Muslim colleagues who now make up nearly three-quarters of the membership of MESA (Nostra) in this country, and who control in most colleges and universities the academic study -- or deliberate non-study -- of Islam.