It seems that more people are learning about Scala. At JavaOne 2009, three of the books about Scala were in the Top Ten best sellers at the conference.
Here's one report [1] with more details.
This review [2] of Beginning Scala is indicative of the quality and general appeal of the books, while Programming in Scala draws many recommendations in Amazon Customer reviews [3].
Links:
[1] http://thediningphilosopher.blogspot.com/search/label/javaOne best sellers
[2] http://www.fearofcode.com/beginning-scala-review/
[3] http://www.amazon.com/Programming-Scala-Comprehensive-Step-step/product-reviews/0981531601/ref=dp_top_cm_cr_acr_txt?ie=UTF8&showViewpoints=1