Have used Fabrik in a Joomla 1.0x environment for a over a year now. But Fabrik 2.0 is killer. I am not sure what the limitations are of this component. If you really need to build a specific application within Joomla, this is the ONLY solution. Plus the support is prompt and very friendly, even to users that haven't paid for support. Watch this one closely, it will change the way Joomla is used.