The best review of the MSCEIT's validity to date is the 2004 article: Emotional intelligence: Theory, Findings, and Implications. Pages 4 to 19 are devoted to the basic issues of validity. Validity evidence is presented that pertains to the MSCEIT's test content, its factorial structure, its convergence and divergence with other measures, and its predictions of important life criteria.
Some more advanced issues, such as incremental validity, are covered in a companion article, A Further Consideration of Issues of Emotional Intelligence.
In addition, new validity studies are arising with some frequency now. These pages will be updated as new information becomes available.