Personally, I learnt RoR and used it for a few home projects, but then switched to Grails, mostly because it runs on the JVM and therefore I am hoping to make use of the plethora of Java performance/profiling programs, which should help identify any bottlenecks in code before they become a problem.
In general I haven't found too much difference in the quality of IDE's used by RoR vs Grails. Although, to be fair, I'm programming on Linux and haven't tried TextMate for RoR development. When I was using RoR I used Netbeans.
Right now I am programming using STS and am finding it a pleasure to use with Grails, although I still find that method detection/completion could be made to work much better.
