1. If can only fire twice because the sun is used up after both shots.
2. It can't move, it's a goddamn planet, not a spaceship.
3. Too. Damn. Vulnerable.
4. I'm sure the cost of the thing was at least twice it costed to build the two Death Stars.
5. Death Star was better in every way...except for that damn ventilation...
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I personally think something more akin to [url=http://starwars.wikia.com/wiki/Centerpoint%20Station]Centerpoint Station[/url] from the "old" Expanded Universe would've been a better idea. It's an ancient superweapon long thought to be disabled. Definitely not every detail of it (some of it was admittedly pretty lame), but the overall idea would've been cool and pretty different from the Death Stars.