I started with HTMLKit. Have tried Notepad ++, SublimeText, and many others. But maybe because I’ve gotten most familiar with HTMLKit, that’s what I find easiest to use. I really couldn’t get comfortable with Notepad ++ and the others I tried.
For me most of HTMLKit’s features are helpful, and I can turn off those features I find inconvenient or inefficient (for example, I don’t like how the autocomplete feature handles a href).
I recently customized the colors so that the things I want to stand out are clear, while those that are less important to pinpoint are more muted. This has really helped.