The only "con" with this plugin (and it may be a browser issue, but it happens on all browsers that I use) is that you cannot do a browser "find" in it (it only performs the "find" on the code that is currently displayed. So I still have and use the built in Atto Html button to do any "finds" in my code.
Now, having both HTML buttons installed I've also notice this (again, maybe a browser issue) - when entering the close by clicking the html button, HTML brings you straight to the bottom/last line of the code, and HTML+ starts you at the top/first line of the code. (OR it could be the other way around). Either way, they start you at different locations upon entering into the HTML... not sure if it's a browser thing or not but wanted to share.