Some features I'd like to see:
-Option to hide global chatters.
-Customizable log options (whether or not to keep one)
-Even minimal ability to visually customize the chat window.
-Option to disallow unregistered guests.
This thing is free, functional, and they have better support for their product than other extentions (like Community Builder). At this point, though, it's not customizable or even a little professional looking. It's probably only useful for personal sites.
And lastly, they ask for a link from your site to theirs. Don't forget to put yours up! It's a simple thing to ask for a good product.
You can disable global features completely.
No log so far, as it takes a lot of space (you can make show room's last 25 messages to incoming chatters tho)
You can use your own CSS to customize look.
You can disable guest access from very beginning of BlastChat release.
We do not ask for a link to our site, but for public link to component on your site (as you can still disable guest access to your rooms and/or disable global features as well)