I believe the holdup with the PC version is due to the fact that the publisher of the DS/PSP versions doesn't publish PC games. Therefore, they apparently made a deal with the developers to keep the game exclusive to handhelds for a certain amount of time. When that time is expired, we should finally hear about the PC version.
My understanding is that the game was originally developed on the PC, but that the portable publisher has exclusive rights for a specified amount of time. Rumor is that a PC version is in the works for late-summer release, but I don't have any confirmed details.