David Zaring has a nice, concise summary of the very different kinds of work that now travel under this heading. Undoubtedly, there has been interesting work done under the ELS rubric, and I have certainly learned from the work by the best scholars in the area (like my former colleagues Bernie Black and Frank Cross, and my current colleagues Anup Malani and Tom Miles), but overall, I know I'm not alone in thinking the empirical fetish has now gotten out of control: there is now too much empirical work being done simply because it looks 'empirical.' There seem to be two central problems:
First, too much of the work is driven by the existence of a data set, rather than an intellectual or analytical point. But the existence of a data set then permits a display of technical skills, which is satisfying to those with a technical fetish. But for everyone else, the question remains: why does this matter? why should one care? and so on.
Second, the analytical- and discursive-skill level of ELS scholars appears to be, on average, low, or at least lower than the typical law & economics or law & philosophy interdisciplinary scholar of yesteryear. This isn't surprising, given that the genre rewards technical skills related to number crunching and data analysis, as well as research design, rather than smarts on your feet, the ability to draw conceptual distinctions, or construct and deconstruct arguments. But the latter intellectual skills are the ones needed in law, both in thinking about law and in teaching law, not the former. Perhaps this is also why discussion of empirical papers typically follows the same tedious pattern of wondering how one controls for this-or-that variable, with the presenter showing, cleverly, how s/he already controlled for it, or admitting that s/he didn't, so that this is an issue for future work, etc.
As always in academic life, the best policy is to let "a thousand flowers bloom," and hope that over time the cream rises to the top (how's that for a mixed metaphor?). But there is the danger that ELS scholars may be on their way to replicating an aspect of the CLS phenomenon of yesteryear, namely, forming a self-reinforcing mutual-admiration society, one which the rest of the legal academy (even we interdisciplinary-minded scholars!) finds increasingly mysterious and disconnected from the central normative and conceptual questions of legal scholarship and legal education.
ADDENDUM: Let me preempt (I hope) what I would have thought an obvious misreading of the preceding: obviously there is mediocre work in lots of genres; the only claim here is that a disproportionate amount is travelling these days under the rubric of ELS, and that it suffers from the flaws noted. That is compatible with the point I made at the start: there is valuable empirical work being done, and by very good scholars with very good minds.