If you like design-based/wysisyg environments, it's great. I like code-based environments, so it also ticks the box for that.
Alternatives exist Notepad++, Aptana, Eclipse, Zend Studio, and the list goes on....
DW may be overkill for 90% of coders - it has all the trappings of a drunken granny trying to look 18. It doesn't has the same functionality as some IDEs mentioned and it is v. bloated with regard to the design side of things, which has absolutely no interest for me.