I finished Lee Smolin's book, The Trouble With Physics. I've been looking at some critical reviews, online, too. Several people mention Susskind's use of a term "popperazzi" to refer to people who make a big deal of Karl Popper's ideas about the importance of "falsifiability" in developing scientific theories, and I think that it is probably accurate to say that Smolin's book is, at least in part, a popperian review of contemporary physics, especially string theory.
I'm not a physicist, nor a mathematician. And I don't really have an opinion about string theory, either way, although I never found it as intuitively appealing as, say, general relativity or even quantum mechanics, to the extent that I understand them at all. In that vein, I'll confess I find Smolin's earlier-enunciated, and currently somewhat academically marginalized, loop quantum gravity theory more intuitively appealing.
But I also would agree with Smolin's critics that his popperian view of string theory is overly combative and ends up coming across as academic sour grapes. It's too polemical to be useful. And I do think that Popper, to the extent I understand him, may not have been the last word on how science works.