COM isn't hot new technology, but it works, costs $0 above and beyond Excel, and can access as much (or more) of Excel.
The reason I ask is that after a quick look, the IronSpread examples don't look too much different than accessing Excel via plain old COM. 
And there's even a chapter in a book  for accessing Excel from Python through COM.
And example code  for wrapping Excel COM in a Python class.
I guess put another way, my question would be what does IronSpread offer above and beyond the regular access from COM?
 http://stackoverflow.com/questions/441758/driving-excel-from... (the second answer)
Implement billing. Now. No excuses.