If I may offer my two cents...
If the purpose in boosting to geosync orbit is to prevent uncontrolled reentry, why not use a reboost to change the HSTs orbit to one that the Shuttle can get to and still make it to ISS? That would keep the HST servicable. It takes a lot more fuel to change altitude to geosync than to change inclination with a minor altitude adjustment.
I sure wish they had boosted skylab. I too would like to see the Hubble maintained. I am just not sure of the cost benefit over other missions, telescopes, etc.