You have to remember, it is just a tool, and that it all it is. They may sell it as a magic bullet, and claim better time to market, but as with all tools, on their own, they cannot help. A tool used badly will still have the same problems as if you didnt have the tool at all. I think if you see this tool as a solution to engineering problems, you are trying to solve your problems in the wrong way. This is not an engineering tool, its just a code converter. Without a good front end design and a large amount of verfication, it wont help.
Ive seen exactly the same sales pitch from mathworks and their HDL coder tool (generating HDL from simulink). It really only works in situations where you dont know what FPGA target you want and all you want to do is number crunching. When it comes to control logic and size/speed optimizations its very poor, and very hard to work with.