Say, you (by you I mean an abstract guy, any guy in your team) have experience of writing and building java web apps, know about filters, servlet mappings and so on, and so on.
Also, let us assume you know pretty well any sql db, no matter which one exactly, whether it mysql, oracle or psql.
At last, let pretend we know Groovy and its standard libraries, for example all that JsonBuilder and XmlSlurper stuff, so we don't need grails converters.
The question is - what are benefits of using grails in this case. I'm not trying to start flame war, I'm just asking to compare - what are ups and downs of grails development compared to pure groovy one.
For instance, off the top of my head I can name two pluses - automatic DB mapping and custom gsp tags. But when I want to write a modest app which provides small API for handling some well defined set of data, I'm totally OK with groovy's awesome SQL support. As for gsp, we does not use it at all, so we are not interested in custom tags as well.