Microsoft did a usability study on a similar grouping of APIs by usage in Visual Studio. The end result was it was harder to find what you are looking for than using the alphabetical ordering. The lesson for API designers: group related methods by prefix so they can be predictably found in code-complete popups.
Prefixing methods is ugly. Methods should be named after what they do.
Squeak (not sure about other Smalltalks) has a thing called protocols: a method belongs to a given protocol and the browser shows it to help you explore your classes. Depending on the method name, the browser can suggest a protocol to file it within. A "sort by protocol" could then be useful in this scenario - provided you had some way to tell the IDE where your method should be grouped.
