I've recently started (re)exploring the world of Groovy and, thus, Grails. The idea of Groovy makes me pretty happy, but Grails kinda makes me cry for a number of reasons. The entire system is, as you probably know, basically RoR but with Groovy complete with scaffolding. The issues with scaffolding are well documented. Most of the scaffolding gets thrown away once you start doing anything "real" and Grails can certainly suffer from that. You can, of course, write your own templates and these templates are basically JSPs implemented with a Groovy flavor. This is where my disappointment really starts to build. JSPs, at least in my circles, are all but deprecated. Even JSF2 is moving away from a JSP-centric view and moving on to JSFTemplating. So why did the Grails guys decide to reimplement JSP? But there's light at the end of the tunnel for me. There are two different projects that give me hope for using Groovy on the web tier: Gracelets and the Wicket Grails Plug-in. Both of these projects have two things going for them:

They leverage existing frameworks and their component sets so we're not left reimplementing everything else as well.
They use more component oriented approaches than JSP development tends to lead to.

I like the dynamic nature of Groovy and the fact you don't need to restart jetty every time you change a class. Maybe these options will make Groovy more palatable on the web. For me at least.