My product remained successful, but they also did quite well too.
Ouch, bad luck! But was this after you published an article or two talking about your success, or was it cloned independently?
The idea that you can build buzz for your product and have the exact same screenshots you're building buzz with be used to trick people into thinking they're in contact with you, but it's some shady fly by night, is just unacceptable to me.
How would you feel if this company http://news.ycombinator.com/item?id=3955265 went even farther than it currently does with it's 'tribute' title and (hypothetical example, not to pick on them!) actually used YCombinator all over its keywords, and had pixel-for-pixel YCombinator's front page, which they stole, to trick people into thinking they're the YCombinator site, and in every way were virtually identical to the confusion of searchers?
This kind of commercial ripoff activity was resolved legally hundreds of years ago. It's unacceptable.