Former member of said cult here.
>Hinduism
Hare Krishnas (or bhaktas, as they prefer to call themselves) don't usually consider themselves Hindus because they reject the caste system and various other appurtenances of Hinduism. They're a monotheistic religion centered on Krishna (specifically not on Vishnu, who fills a sort of father-god role and is considered an avatar of K.). They sometimes bill themselves as a "lifestyle religion," which is by definition cultish. In my experience, I saw very little of the normal creepy cult things, like outright brainwashing, bilking of money, personality worship. Srila Prabhupada is long dead (well, everyone is immortal in Hare Krishna, but from a secular perspective dead), so you don't have to worry about Manson-style cult of personality, unless you're in Hawaii where a fringe Hare Krishna sect has enormous political and social power, and its own spiritual leader.
>As It Is
How much did you pay for Bhagavad-Gita As It Is? I've been to temples all around the northeast and some abroad and all of them sold the book at practically production cost, i.e., about $10 for a 500-page book. It's also totally free online at asitis.com. So I doubt you were being bilked as far as the donation is concerned.
>Translation
It's pretty great, actually, but only if you want to know the deep spiritual side of the Gita, not the straight literary side. (I'm a Sanskritist, btw, which I got into in part because of Hare Krishna, which I joined as a teen, but have kept up with long since leaving the cult.) The nice thing about As It Is is that there's the original Sanskrit text, then a word-for-word translation, and then a fair translation. This means that even if you just know a little Sanskrit, you can practice with it, and it's extremely helpful for keeping track of words that have multiple meanings, such as atman.
But as Prabhupada said, what mattered was not the translation so much as the "purport." That's the semi-arcane term he uses for his commentary. The translation of a given verse might be 150 words long; the purport is often thousands. That's why I say you have to want to learn the deep spiritual side of the text. He's not presenting it as "a scene from the Mahabharata," but rather, the central philosophical text for all Indian (or actually world) religion. So he cross-references dozens of other Sanskrit documents and includes his own essays in there on how you ought to live your life, the shape of the cosmos, the functioning of karma, etc. If you're interested in religion and philosophy, you'll probably get a good kick out of it.
Because the Hare Krishnas sell this edition at such a low cost, it is probably the most comprehensive and yet affordable edition of the Gita out there, but just keep in mind that you'll be studying the text "from the inside," as written by a fervent practitioner of yoga, not a Western academic.