I'm a few chapters into part 2, and enjoying it so far. I was a little sceptical about Soong showing up (new android body aside), because revealing characters presumed long dead to actually be with us still, only hiding, is difficult to pull off even for an author as good as Mack (for all that it's consistant with Soong's behaviour). However, part 2 is reassuring me so far, because any objections are being soothed by the great first-person insight into Soong's character. I don't recall Mack attempting this before but thus far it's very successful. I guess that's the first reminder that tricky plot elements can be swallowed easily if the writing is good enough. Whether the novel will pass the second round of that test when a certain someone is returned to the ranks of the functional in...some capacity (yes, I've been reading some of your spoilers)...well, I'll have to wait and see.
I've got a sneaking suspicion that I'm going to be left in an uncomfortable place regarding it; I'll explain more, naturally, when I've finished the book and discovered if I'm right or not.