A User of Paragraph Styles+
Given the limitations of the Google Docs API, Paragraph Styles+ had to make a lot of compromises. It might be worth the compromises, but they're pretty harsh.
You need to use it's custom sidebar to set formatting, and the interface is clunky. There is no equivalent to "Update this style to match". There is no way to see what style is applied to a given paragraph.
If you try to manage the Google Drive built-in styles with Paragraph Styles+, it will completely stomp the Google Drive settings. So either exclusively use Paragraph Styles+, or avoid the built-in styles inside of Paragraph Styles+
The available fonts are fixed; you can't add arbitrary fonts from Google Fonts as you can in core Google Docs. I imagine fulling connecting it is difficult or impossible, but perhaps it would be possible for someone who is desperate enough to provide a link to the Google Font's stylesheet?
The margins and spacing must be set, or it refuses to let you save a new style. This wouldn't be a problem, but it doesn't default to "0", but to nothing at all.
The margin setting for the first line is a bit odd. I believe most word processors specify the first line indent relative to the left margin; so hanging indents are implemented as negative numbers. Here, the first line is completely unrelated to the left margin.
The margins and spacing are specified in points, which is a fine system, but it's unfortunate that I can't use em, in, or mm.
As far as I can tell, there is no way to set the paragraphs background color. You can set a "highlight" color, but that's very different. I'm looking for give the entire block a single color, the way you would use Format > Paragraph Styles > Borders and shading... > Background color in core Google Docs. The same goes for borders. This make two of my use cases difficult: I can't put a border on the left edge of a blockquote, nor can I have example blocks with a different background color to make them distinct.
If you are in the middle of a custom style and start a new paragraph, the new paragraph won't keep the Paragraph+ style.
For me, it's not good enough, but I imagine some people will find the tradeoffs worth it.
(Minor note to the author: the line spacing should be "single", not "simple.")