I'm kind of neutral on the issue, because I'm not that good at bullet hell games since I played Touhou. I would like to see Cave's shooters come stateside, simply because Cave has a good fanbase over here as well, and we Americans love to shoot stuff (regardless if it's insects, steampunk machines or modern-day machines).
I'm also for a PC version of the games too, if Cave is willing to do that. Keyboard > gamepad for shooting games simply because I grew used to using them. Easier to tap dodge too. =V
EDIT!
@Matsuri: That would be a viable option if it weren't for the fact that Imported 360s cost more than US ones, and the DLC for JP 360 games is ZOMG EXPENSIVE (at least the Otomedius DLC is).
@Ghaleon: Because the 360's practically a PC. Would you rather they port to the PS3?
@Observer: Slowdown is the reason why most bullet hell games are possible to beat in the first place. Removing that would be like removing the ability to fuse demons together in MegaTen--it's crazy and not a good idea.