I'm often saddened that because CLOS doesn't use a message-passing paradigm (and because Lisp's syntax is prefix?), doing traditional Intellisense-style method listing and completion is nearly impossible.
I wouldn't be impossible, it just wouldn't work the way a message passing language does. If you ask me the trade off wouldn't be remotely worth it.
You could e.g. have a system where write some type name (or variable with a declared type), hit a key and get a list of all the generic methods that apply.
It would be a small matter of programming to add a function to Slime that, upon typing a symbol presents a list of every function that's reasonably likely to apply to it. I think the reason I haven't seen it is that it represents a very noun-oriented way of thinking about programming. Lispers are less likely to program that way than say Java programmers, where the language enforces the style.
