Recs.
Updated
A popular commercial IDE with a free community edition.
Both Community and Ultimate Edition have support for:
Clojure, CloudSlang, Dart, Elm, Erlang, Gosu, Groovy, Haskell, Haxe, Java, Julia, Kotlin, Lua, Perl, Python, Rust, Scala, XML/XSLT and R.
Sadly only the Ultimate edition has support for JavaScript, HTML/XHTML/CSS, PHP and Go.
SpecsUpdate
Pros
Pro Smart refactorings
IDEA places an emphasis in safe refactoring, offering a variety of features to make this possible for a variety of languages.
These features include safe delete, type migration and replacing method code duplicates.
Pro Intuitive and slick UI
IDEA has a clean, intuitive interface with some customization available (such as the Darcula theme).
Cons
Con Somewhat expensive
IntelliJ IDEA is fairly expensive, with a pricetag of $149/year.
However there is a free community edition available.
Con Version controlling configuration is painful
They have a mess of random XML files without much documentation. Also, sometimes these files change all the time (mixing state such as window sizes and configuration) which makes it difficult to version control them.
They haven't been all receptive to suggestions to improve the situation. For example see:
https://youtrack.jetbrains.com/issue/IDEA-154157 (improve docs)
https://youtrack.jetbrains.com/issue/IDEA-184637 (improve workspace settings)
However, they are working on not saving useless system defaults into the user's configuration file: https://youtrack.jetbrains.com/issue/IDEA-128660
Con «standard» hotkeys behave differently
Seems like hotkeys assignment in Idea have no logical consistency.
Like «F3» is usually next match, «Ctrl+W» - close tab, etc — they map to some different action by default.
There is a good effort in making the IDE friendly for immigrants from other products: there are options to use hotkeys from Eclipse, and even emacs. But these mappings are very incomplete. And help pages do not take this remapping into account, rather mentioning the standard hotkeys.
So, immigrants are doomed to using mouse and context menus (which are rather big and complex).