"Superficially religious" seems fair, but I object to the "essentially religious" characterization. What makes religious claims essentially different from other sorts of claims is when their advocates say they exist in a "separate magesteria" where the normal rules of reason and empiricism don't apply, fail to recognize that extraordinary claims require extraordinary evidence, etc. (in other words, the essence of religion amounts to failures of rationality--if your idea of "religion" amounts to "woo, I don't know, that sounds pretty fantastic" then I don't see why things like supersonic air travel, cell phones, etc. wouldn't count as "religious" phenomena, at least to people who lived long before they were invented).
By my reckoning, Sagan's dragon in his garage is the opposite of transhumanism--it's a claim that doesn't look superficially all that much like most religious claims, but it's an essentially religious one because of the rationality failures Sagan exhibits in his attempts to defend the existence of his dragon. You talk as though there is some well established body of thought explaining the rationality failures behind transhumanist claims, but I find it a bit suspicious that you're not linking to anything and the best you seem to be able to do is draw what looks like a superficial analogy between transhumanism and religion... if you know of a better argument, please by all means share it.
(I think the best you could do would be something along the lines of extraordinary claims requiring extraordinary evidence, which I'll accept... I should have used "likely" or "plausibly" in order to qualify my claim, and I do think the transhumanist community is a bit overly attached to specific scenarios, but they still seem to me like important possible scenarios to consider and plan for. The alternative looks a lot like sticking our collective heads in the sand and pretending that there's no chance at all that trends will keep going in the direction they've been going.)
What makes religious claims essentially different from other sorts of claims is when their advocates say they exist in a "separate magesteria" where the normal rules of reason and empiricism don't apply
Proving God's existence on the basis of reason and empiricism was very popular only a few centuries ago. Were not these pieces of theology religious?
I don't see why things like supersonic air travel, cell phones, etc. wouldn't count as "religious" phenomena, at least to people who lived long before they were invented
They would certainly count as magic.
A blog post by Athrelon on More Right.