This one may look like an interesting reason to use Steam but that's not enough games ported to Steam from the arcades. It is somewhat likely that most of those games have been ported to the consoles from the arcades for some reason and PC gaming is somewhat a different story. There are also games in the same style as well but they are actually in the consoles and mobile devices, not Steam. Also, recently, it seems that Arc System Works had also joined Steam in addition to Capcom and SNK Playmore doing so for their upcoming fighting games released for the service, be it the old one or the new version of the old game.
For Treasure, it might be their recent entry to Steam with the first game for it being Ikaruga. It is based on Nesica X Live release as we saw from the screenshots such as the in-game interface, the title screen, achievements and so on. There's even the vertical and horizontal screen support as well as multiple screen ratios. The major enhancement in HD is probably from XBLA port which has better lightings, different colorization for the models and the sprites that are said to be taken from Gamecube version. From the Nesica X Live version, there are additional programming stuffs done to Chapter 3 and 5. Also, the game start screen is completely different compared to the original arcade version which displays the ship along with the pilot.
The Steam version is likely to be released this month and that took the small developer team the longer time to improve the quality of the game like porting from Nesica X Live version to Steam. If only the XBLA version has the patch to match the Nesica X Live version in the future, then we can see additional programming enhancements done to the game.
