Hi Marc,
I wish you the best of luck with Agora, but in all honesty, most users aren't tech savvy enough and don't understand (or agree with the reasons) why they can't have a flashy looking template/site. Unfortunately, it's not enough to tell them why, because if they don't accept/understand your answer, you can bet that their end users (who don't understand anything at all about website construction) won't either.
Just look at the success of template providers such as RocketThemes etc. Most Joomla admins want a website with all the bells and whistles and aren't particularly concerned with the ins and outs of PHP coding or the small development teams' woes of a missing apostrophe causing an error in a script.
This is the reality of internet users.
I feel that what you might end up doing here with Agora, is spending a lot of time producing a technically perfect Joomla component that not many people end up using. You need to ask yourself if that's what you want to do over the next couple of years.
Let's face it, if vBulletin suddenly announced that they were giving away free licenses and had also developed a component to integrate the forum software into Joomla sites, nearly everyone using Joomla would choose that. Why? Whilst you may have coded a perfect forum, people just want more bells and whistles!
There is a forum software rapidly gaining popularity called myBB (has over 15,000 members) which is just like vBulletin, except it's FREE and OS. They have already managed to produce a bridge for use with Joomla, and seem very helpful towards Joomla users. Now imagine if you and your team of 4 developers were to use their code (as in all of the hardwork has been done for you in creating a forum that is like vBulletin), and simply dedicated your time to integrating it as a Joomla component (rather than it having to be run as an external link or in the wrapper).
THAT would be very popular! Pretty soon, you'd find that the user uptake on it would be rapid, and that the other component developers (community builder et al) would happily provide modules that worked with your forum component.
But as things stand with Agora, I just can't see it really taking off. My feeling is that people don't want to wait while a whole new forum system is developed (that let's face it, will always be behind in the feature lists of the big names). They just want something exactly like myBB, vBulletin etc. to work inside their Joomla installation with the minimum of fuss but with as many bells and whistles as possible.
Sorry if it's not what you want to hear, but I just thought I'd share my experience and opinion on this.
