Robin2, I get that you are a passionate advocate of the Arduino IDE, but you are not addressing my question. I would be delighted to hear from you again if you can, but I don't need evangelising.
I am trying to make an objective decision on whether to invest my time in a tool which seems to have limitations, and from all I've seen of it appears to be an obstacle to making the best use of the hardware. I want to evaluate the benefits of the Arduino architecture, both hardware and software, without the apparent capability ceiling inherent in the sketch approach. Bear in mind that from my perspective I'd already be downgrading from Xmega to Mega and downgrading the IDE as well would make Arduino a retrograde step for me. Perhaps I'm barking up the wrong tree with Arduino, but I'm hoping not.
If the sketch system and the Arduino IDE are prerequisites for using the Arduino architecture, then can anyone make the case for it for advanced users?
Otherwise, if these are not prerequisites, what alternative routes are there to using Arduino free from these constraints?