spring + groovy + grails = ?

Just read that Springsource (“Weapons for the War on Java Complexity”!), Rod Johnson’s company, has acquired g2one, the company behind Groovy and Grails. Looks like there’ll be 2 major Java development stacks; all things JSR/J2EE on one hand and Spring/Groovy/Grails on the other? What train should one hop onto, when having to choose a new web development framework?