Also, in the manga, Mahoro doesn't die. At least not permenantly. She's reincarnated through Matthiew's power as a human, and after 19 years or so, when she reaches the age she supposedly was masquerading as when she was an android, she returns to the older Suguru.
Plus, when Mahoro "died", it wasn't just to take out that android kid. It was to destroy several huge fragments of the moon that would have destroyed the Earth if they'd hit, blown off when the earth forces tried to attack Saint's mothership. Makes it seem a lot less pointless.
Also, Suguru's a Vesper agent in the future in the manga version, and the future itself isn't at all depressing like it was in the anime. Plus, they follow up on what happened to several of the other characters in the show. (Chizu became an author, for example).
Anyway, yeah. Anyone who liked Mahoromatic owes it to themselves to read the manga.