Well, I haven't tried Intellij, but in my experience the best coding environment is:
1. Visual Studio
2. gEdit
Visual Studio has incredibly good fuzzy code completion and gEdit has a total lack of features to be confused by and good font rendering. I just look at all the menus and buttons in Eclipse and I can't stand it. All this stuff can't possibly be necessary.
Since VS is not available for neither Scala nor Linux I'm left with gEdit.
IntelliJ keeps most of it's buttons hidden (in v13 at least). Might be worth a shot. I'm not entirely sure what you mean by "fuzzy code completion", but IntelliJ supports case-insensitive-in-order-partial-symbol matching.
For example, "jsfmt" with match "jsonFormat", and display the matches as I type so I can arrow-down and hit ENTER if I see what I want (or just keep typing until the list filters down to the one I want).
Implicit invocations get underlined by default as well. Which is nice since I'm rarely at loss for understanding what the compiler is doing to make this code work.
With fuzzy I mean that I can search for "tunnel" and get "channel". It does sound fuzzy, unless it's hardcoded. Code completion in Eclipse isn't fuzzy, so "temrinal" doesn't get you "terminal". In Eclipse it's basically just a regex.
Visual Studio has incredibly good fuzzy code completion and gEdit has a total lack of features to be confused by and good font rendering. I just look at all the menus and buttons in Eclipse and I can't stand it. All this stuff can't possibly be necessary.
Since VS is not available for neither Scala nor Linux I'm left with gEdit.