VEERS: My lord, the fleet has moved out of light-speed. Com-Scan has detected an energy field protecting an area around the sixth planet of the Hoth system. The field is strong enough to deflect any bombardment.
VADER: (angrily) The Rebels are alerted to our presence. Admiral Ozzel came out of light-speed too close to the system.
VEERS: He felt surprise was wiser...
VADER: He is as clumsy as he is stupid. General, prepare your troops for a surface attack.
I don't think there's necessarily anything wrong with being able to raise a planetary shield too strong for conventional orbital bombardment to break, provided troops can still land. If nothing else, you can blockade the planet. And if there's no gravitational shield facility, the Death Star can still blow the place to smithereens...
[This message has been edited by BeeDee10 (edited 14 June 2001).]