1) Joomla newbies: the Chamaleon engine is very powerful, but as every automatic process it could lead to unexpected results (or your template could be unsuitable for it). You have to try it in order to find out the result, you could need to write your own css directives or modify your template (or ask support to the team, which is great)
2) Advanced user: many features have to be added in Ninjaboard to fit advanced requirements: Lock/unlock forum, set a sticky post on top, insert ads between the posts, integrate a captcha system (you can use third party extensions, but I would prefer an integrated solution), a forum search engine (there is a plugin to integrate results in native Joomla engine, but I don't use that native search!), a forum menu item for profile management (I could not find in the backend) to and so on.
To make it short, you have to try Ninjaboard to find out wheter it fit your needs or not. It is very easy to install and manage, the look and feel is great and if Chamaleon loves your template, it will perfectly merge you look&feel.
I'm really looking forward for 1.2 version, I'm sure it will fill many gaps
Sliding and fading effect are also parametrizable from module parameters.