Thoughout the latest Arc of Bleach there has been much info of these resurreccions from the Espadas.
I thought that on arrancars can only use resurreccions but lately other beings can use them else!
Like Ichigo, who went through his resurrccion and unconsciously used it and controlled by hollow Ichigo.
And the Tousen guy who worked with Aizen, he can use it but he's already pwned
Anyway it seems that there are still mysteries about this 'resurrcions'
By the way Grimmjows resurreccion is one of my favourites.
Tell me some more info and your opinions about resurrcions and or guess who else will use it!