boost converter with current mirror feedback and type II compensator?

http://www.flickr.com/photos/26914086@N05/2808260220/sizes/l/

I wonder why to use a current mirror here? the internal ref. V = 1.26.
the current mirror calculation is correct I verified.
But why use a current mirror here? keep from transient voltage?
temperature compensation?

if add this current mirror, how to calculate the compensator? here is
a R-C in series, is't a simplified type II ?

calculation for the compensator is welcomed.
.