As mentioned by others, it's pascal implementation and p-code concept were pretty cool. But it left a lot to be desired as an operating system. For example, IIRC, files had to be stored in continuous blocks on the disk and management of blocks were up to the user. If your file needed 10 blocks then you needed to find a hole on the disk with at least 10 blocks... which meant you might need to move other files around to make enough that hole.