I came across the Pronunciation Patterns web site through a sponsored ad while reading Gmail.
I'm glad it promises only to reduce your accent, not teach you correct grammar... because if the program taught you the kind of grammar found in the site's FAQ page, even the most perfect accent wouldn't convince listeners that you were American. (Sure, even native speakers make errors when speaking or writing, but the kind of errors a native speaker makes are different from the ones learners make, and these are the latter kind.)
Constructions such as "I have trouble with the TH sounds. How can I solve it?", "Does Pronunciation Patterns provides step-by-step lessons to help me learn English Pronunciation?", "Can Pronunciation Patterns help me reduce accent to be more like American accent?", or "When does the letter T is pronounced as the D sound?" (that last one sounds the worst to me); or the (to me) stilted use of "shall" in "How shall I use Pronunciation Patterns and how often shall I use it?" or "Why shall I buy Pronunciation Patterns today?"—it all seems very "eek" and foreigner-speak.
I think it makes the site seem unprofessional; they're selling a product but they clearly couldn't afford to hire someone to proofread their website. Even if what they're selling is not advice on grammar, that page (for me) reflects poorly on the product.
(And I just noticed that the little flags at the top of the FAQ page link to… machine translations of the page via Google. Er. …and the one for German doesn't even work since they put a ? where a & belonged!)