Wow. You're lucky to be reading that book for the first time... it's pretty amazing, although I bet a lot of the "gee-whiz" tech will seem pretty dated today. just keep in mind that it was written before using a mouse to click icons was an everyday affair for computer users...
In order to answer your question about possible Marathon connections, I'd have to spoil the story for you a little... I can say for now that Durandal's rampancy and attempts to escape would not be very out of place in any of the first three "Sprawl" novels by Gibson. in a way, Durandal and Neuromancer have a lot in common.
If you don't mind a sort of spoiler for the story let me know and I'll post a more explicit link for you, but it's a) still pretty tenuous and b) will possibly reduce your enjoyment of the books a bit.