Well, it is disappointing, but in a mildly educational way. Let’s analyze this latest arc of Superman/Batman.
In #57, we had the promising set-up, in which Superman is shrunk down to nano size. Batman undertakes to rescue him, adding to the urgency by noting that time passes much more quickly among the extremely small and if something is not done fast Superman will die of old age. (I surmise that this is a comic book factoid he picked up from the Atom; I sure don’t remember reading anything about it in SciAm or the NYT.) In #58 it is revealed that the nanoverse is populated by warring factions which conveniently break out into bad guys and good ones; the bad guys tinker with Superman’s metabolism which, again very conveniently, turns him against Batman. In this issue #58 Batman rapidly cures Superman and they defeat the bad guys and are canonized by the good after their departure for the larger universe.
What is lacking? The almost Dickensenian role of coincidence has to be ignored as a standard feature of comic books. But even aside from this, there are major flaws in the plot. Since the time dilation effect is not noticeable once you are microscopic, it passes right off the radar. Batman neither worries about it, nor tells Superman about it so he can worry — so there is no cost to the characters. And since there really is no doubt that the two will prevail in the nanoverse, there is no suspense. These two factors are essential to any story — if there is no cost then nobody cares; we might as well be reading about the selection of dental floss flavors.
What this story needed was at least one hairpin plot turn, to increase suspense, and for the time dilation card to be played properly, to make the cost clear. And, to make the leap into greatness, it needs a twist at the end. What is so annoying about it is that I can see how it should be done. It would be an interesting exercise to rewrite this, properly. Had we but world enough, and time! Unfortunately nobody is likely to shrink me down into a nanoverse so that I can get a lifetime into one day.