I use it, and it works well for the amount of coding I need to do- not a lot. It does seem to have a lot of features, but I haven't explored all of those yet.
Never heard of Notepad++ is slowing down the computer? You may check out other issues, as I don't think using Notepad++ will slow your OS.
BTW I use Notepad++ for variety of reasons. I use for minor HTML edits for my webpages, I use it for building new webpages. I also use to list data from relevant sources using Notepad++.
Yep, this is a very good tool. 🙂 Most of the people I know at work also use this for data files and whatnot. I don't use it for code very often, though. Mostly use IDEs like phpStorm, NetBeans, IntelliJ, and sometimes brackets.
I also concur that Notepad++ won't slow down a computer, unless you try to open up some really big files in it. If you open up something more than a few megs in size, then you can definitely run into slowness. That's true for any file editor though.