In 7.x, I frequently use "complete word", but it appears to be gone in 8.0. "Complete Word" has advantages over "cyclic expand word" - it allows camel-case expansion and presents you with a list of all the possible completions. Am I missing something or was this functionality removed?
In case you are wondering why the need comes up, I code a lot in Lua for my work. Even though Idea has no direct support for Lua, Idea still works as a decent editor for Lua (just enabling .lua as a file type and designating the reserved words for syntax highlighting).