I don't have a big problem with their ideas about AI just because they're so disconnected with reality. I mean, if we go another thousand years without an apocalypse, it seems more or less bound to happen, so in the abstract it is something that should be investigated; however, it's so far off now that I'd lay serious money that all of their theorizing will be pretty much useless when the first implementations come around. In fact, since I've read and understood the Basilisk and said so publicly, you could fairly say I'm willing to stake my life on that :) I suppose I can only have faith that, when it comes about, people will do their best to make it all work out OK.
The argument I'm making about memory is that when communication has become advanced enough, you can't make a clear distinction between inter-generational memory and meat-memory over a significantly long lifespan. People change over time; give it enough time and you're as different from yourself now as your great grandchildren will be.
I don't think we need long-lived human beings or human personality constructs to gain the societal advantages of "I remember when..." It's feasible today for a person to record and archive audiovisual, geospatial and limited haptic data of their entire life experience, beginning to end. We can't record your thoughts, but if they're important you can write them down. I'd also wager that we'll see almost fully convincing sensory recording, which is a plain prerequisite for uploading, well before any life-extension technology which deserves the title of immortality. It would then be unrealistic for your descendants to say that they remember the things that happened to you only because these recordings would be far superior to memory.
Of course, the only issue is that we've had this sort of thing for a good while now, and it turns out we just aren't that interested in the things that happened a long time ago, just like, aside from the highlights, I don't care that much about what happened to me ten years ago.
Ten years ago, of course, I thought that everything that was happening to me was quite important.[0] That's why I label this idea of immortality "greedy"; it represents the whim of a brain state at the present moment to continue to influence the world long after it has become irrelevant. Just look at the current state of US politics to see where that gets us. (I've never seen a transhumanist argue that every transient state should be preserved in perpetuum, but I'd be curious to know what they tend to think about it.)
The point being that if uploading constitutes a form of immortality, so does having kids; the same theory of consciousness underlies both.
[0] This is a bit of a tangent, but I think this is (most of) the reason that burial rituals are one of the cornerstones of human society. Obviously it doesn't matter to the dead person what happens to them, but it is crucially important for us to have a say in what happens to us; we hope that, if we respect our parents' wishes after they die, our children will respect ours. And we take this so seriously that, in fact, they do.
I suppose I consider transhumanism, especially cryonics and uploading, to be a very highly developed burial practice. If it is the wish of a dying man to have his brain frozen in nitrogen, I will respect his wish, and even humor his beliefs about what that might mean. But I don't believe it means any more in reality than if we stuck him in the ground with everyone else.
And yes, I recognize the irony in writing this much about something I think is silly to spend time thinking about :)