President Masato Maegawa told assembled press that Treasure had worked for about half a year to get the game running on Xbox in a way that closely resembled the Saturn version. Some elements had to be reprogrammed, because they relied on Saturn hardware features.
Speaking of Saturn adaptations, the XBLA remake will have user-selectable transparency levels. Because the Saturn couldn't handle "real" transparencies, it used screen-door style pixel meshes to simulate it. If you want that authentic Saturn feel, you can use those, or you can opt for true transparency effect.
More modern additions include online co-op, and an Ikaruga mode that implements the "chain combo" scoring system from that game, and is only playable if you have at least one achievement in XBLA Ikaruga.