I absolutely vote thumbs-down on Notepad++ because it has a major bug that the program's author, Don Ho, refuses to fix. The bug causes the following problem: when saving a new document, your new document is saved without any extension. So, for example, if you create a new plain-text document, it is saved without the ".txt" extension, and therefore it is saved by Windows as an unknown file type, which Windows will not know how to handle when you try to open it. There is a work-around for this bug, but the work-around is a time-consuming hassle that you must remember to do (and probably won't remember to do) every time you save a new document.
Here is a link to a bug report about it (on an official Notepad++ web site):
Scroll to the "Followups" section at the bottom of that bug-report page, and you will witness Don Ho blatantly refusing to fix this major bug. And what reason does he give for not fixing it? He says it's too much "coding effort". Well, it's too much user effort for me to tolerate this horribly defective program. Goodbye to Notepad++; I never want to touch it again.
By the way, Notepad++ Portable has the the same major bug. I am disappointed to see John Haller, who otherwise has a reputation for high-quality reliable software, promoting this fundamentally flawed program. After all, what is more fundamental than saving a new document?!