Is it worth patenting a software product?

The scope of your patent protection is determined by the claims. Patent attorneys try to draft claims that are difficult to design around, whether technologically or by making the design-arounds we anticipate economically less competitive. But the claims are typically amended and narrowed during the examination phase so at the time you make the patenting decision there's no way to know how broad your eventual patent coverage might be, or how hard it would be to design around your claims. Sorry, but that's just how the patenting process works.
BTW, if someone makes only a simple modification to yours, theirs is not patentable if that modification is an obvious one.

Your question is no different for software or hardware patents, so it is the same as asking, "Is it worth patenting a mouse trap when someone can make a simple modification and patent a different device that does the same thing (traps mice)?" When you think of it that way, it makes more sense. The essence of writing patent claims is to draft them in such a way that anyone who tries to duplicate the invention will infringe the claims. The "invention" in a software patent is not the way that the software is written, but is instead the end result of what the software does. So, the answer to your question is, yes, it is definitely worth patenting a software product, as long as what it does is novel and non-obvious.