Fighteer: Some logical issues that were never addressed to my satisfaction in the story.
How the Other deals with time lag. No matter how powerful the hardware running Otherland is, the fact that it has to communicate with a geosynchronous satellite housing its "operating system" should add a minimum half-second to the system's latency. The only justification that I can remotely imagine is that the Other's psychic powers make people fail to notice the lag or compensate for it somehow, which implies that (a) psychic power travels faster than the speed of light, (b) the Other is precognitive as well as telepathic, to react to information transmitted by the network before it actually arrives. I can also imagine Otherland being asynchronous, given the fact that the majority of the hardware is on Earth, which would imply that the Other has more of a supervisory role in managing the system rather than acting literally as its CPU. Still, characters specifically remark on not experiencing even the slightest bit of latency while in Otherland, and one of the effects of the Other's destruction is that they begin experiencing it again. So, Psychic Powers are implicitly FTL?
Precisely how the Brain Uploading mechanism works. Specifically, Jongleur is careful to exposit that every member of the Grail Brotherhood was fitted with a neural implant that duplicates their brainwaves, allowing the Other to build a layered copy of them including their entire personalities. Paul Jonas was also presumably outfitted with such a device, although why they'd waste such expensive technology on an expendable pawn is slightly baffling. However, Orlando and Mr. Sellars have no such implants and certainly don't acquire them within the story; in addition, they spend far less time in the simulation than the members of the Brotherhood. So, how is the Other able to upload them with equivalent precision? Is all the hardware and time merely a Magic Feather, with its Psychic Powers able to take a complete mental imprint of a person in a matter of days (or hours in Sellars' case)?
If I remember correctly, Paul was Jongleur's test subject for the brain uploading process, so at least the part why he got one device is explained. Sellars implants may have the same functionality as the device (but that's just guessing on my side).