There are lots of free editors out there; if Notepad++ works for you and you like it, you should use it. I used to use Notepad++, but I do not anymore.
I wanted a cross platform editor. I like having a the same workflow at work (Windows) and home (OSX and somtimes Linux). One license gets me going on all systems.
I don't care if I have an IDE. I like using my editor and a good file search app like grepwin on windows.
I like the command palette concept.
I like the goto anything concept.
I like that the plugin system is in python, it makes plugin development more accessible for people to pick up, which is why Sublime has so many plugins available https://sublime.wbond.net/
I generally like how flexible it is for me to set it up how I like.
It does have some bugs, but none that really cause major hiccups or that I notice much.
The syntax highlighter system isn't always the best, but it works pretty good; it is the same that TextMate uses.
Sublime works for me. I could get my company to buy me SlickEdit, but like I said, I wanted a similar work flow at home (I am not paying $300 for an editor).
Sublime workflow is better for me than Notepad++ (but Notepad++ is a very solid capable program). I can quickly code up my own plugins when I want something specifically. I can use it on all platforms. $70 is more affordable than $300.