Coming from VS I love netbeans for writing Rails code in.
I became very spoiled by Visual Studio's ability to let you explore libraries via intellisence. Netbeans is the only Ruby IDE I've found that comes close to letting you do that.
IDEA does that rather nicely. Its maven support can reduce your box to a paperweight when it reindexes, but other than that, it's a very nice product indeed.
If you're not working on a complex codebase, it is total overkill though.
I became very spoiled by Visual Studio's ability to let you explore libraries via intellisence. Netbeans is the only Ruby IDE I've found that comes close to letting you do that.