I don't get the feeling that a superior intelligence is going to be so petty as to just waltz around the universe sucking up resources.
Sucking up resources? Nobody else is using them. They're just being wasted; hastening the heat death. One star will only last billions of years. All the matter in a galaxy could be organized to support a larger civilization for much, much longer.
After all, any post-Singularity Society should realize that the ultimate goal of their intelligence is to merge with the rest of the universe.
You are making a claim about a very large portion of possible minds. Also, I don't even know what you mean by "merge with the rest of the universe."
Why would that mean that they must eliminate all other intelligences along the way, rather than using those intelligences as a proxy to complete the task of total utilization of the universe's energy.
First, aliens that evolved separately wouldn't have similar values. Some of them would actually be threats if they valued paperclips above your civilization. Second, automated probes can do a much better job of organizing matter than some random apes with nukes.
My point is that we do not yet know enough to even begin speculating on possible motivations for ET, until such a time as we can sort of terrestrial motivations among our respective intelligent species.
Actually, yes, we do know enough to speculate. We notice that everywhere we look, there is no evidence of alien intelligences. The lights are on but nobody's home. So there are three possibilities:
Every civilization that has ever come into existence destroys itself.
Every civilization that has ever come into existence "transcends" in such a way to make the universe indistinguishable from ordinary stars and galaxies.
There aren't any other civilizations in our observable universe.
Sucking up resources? Nobody else is using them. They're just being wasted;
I'd like to point out that even among the forms of intelligence that we have met, this is not a universally compelling argument. Consider that many people have a strong negative emotional reaction to the idea of putting garbage on the moon (assuming this could be made efficient). Now, objecting to this makes precious little sense. The moon is huge: even if we decide we want a colony there later, we're unlikely to coat its entire surface in waste and leave no room there. In fa...
An uplifting message as we enter the new year, quoted from Edge.org:
A few thoughts: when considering the heavy skepticism that the singularity hypothesis receives, it is important to remember that there is a much weaker hypothesis, highlighted here by Tegmark, that still has extremely counter-intuitive implications about our place in spacetime; one might call it the bottleneck hypothesis - the hypothesis that 21st century humanity occupies a pivotal place in the evolution of the universe, simply because we may well be a part of the small space/time window during which it is decided whether earth-originating life will colonize the universe or not.
The bottleneck hypothesis is weaker than the singularity hypothesis - we can be at the bottleneck even if smarter-than-human AI is impossible or extremely impractical, but if smarter-than-human AI is possible and reasonably practical, then we are surely at the bottleneck of the universe. The bottleneck hypothesis is based upon less controversial science than the singularity hypothesis, and is robust to different assumptions about what is feasible in an engineering sense (AI/no AI, ems/no ems, nuclear rockets/generation ships/cryonics advances, etc) so might be accepted by a larger number of people.
Related is Hanson's "Dream Time" idea.