I've been using Eclipse for years now, and like a lot of others, I find myself at home when using that standard editors. At the same time, I'm aware that there's a big portion of software developers out there that rather using Vim and such. And some people would rather you could do more when working on source code in Eclipse. Perhaps SlickEdit is what's missing from your setup.
I've always assumed that SlickEdit was a tool for Vim nuts to get their key bindings into Eclipse. That's one aspect of it, but there's more. For a start, you get new views available when editing your code:
As you can see, it's not miles away from what you get with Eclipse anyway, but it may help increase your productivity somewhat.
As I said, you can get Eclipse to work like your other favourite IDE / editor, through the available keyboard emulations. So you can use Eclipse like Xcode or Visual Studio, Emacs or Vim.
One of the things I really liked about SlickEdit was the Recordable Macros. Now and again I have to do repeatable, mundane tasks within Eclipse. I know I should aim script anything that I do more than once, but that's easier said than done. At least now, I can record the things I've done, and re-run that macro later.
I thought the diff tool that's supplied worked pretty well. Usually for directory comparisons I'd like WinDiff, outside of my IDE. But the DIFFzilla tool is a pretty good alternative, and you don't even need to leave the comfort of your IDE to use it.
One last thing - if you use some custom DSLs, you can get SlickEdit to provide support for color coding and keyword definitions. This saves you from needing to write your own editor plug-in for Eclipse if all you want is some basic support.
It's not free - you'll need to pay a license of $99 per user per year to get all these features. But you can just give it a test run and make sure that it fits your requirements. SlickEdit also provides a really nice standalone editor too, that worked out great for quick scripting tasks, where I didn't want to fire up Eclipse.