Have you looked at Sublime Text 2?

http://www.sublimetext.com/2

I switched about a year ago and I am very pleased.

EDIT: This shows it off better: http://www.sublimetext.com/

Okay,

suppose this line:

    result = someFunction(param1, param2='ok')

mouse over to `someFunction`, a small box shows brief description of function, what it does, how many parameters are required, what does optional parameters do.

It's basically a richer version of <span title="text" alt="text"</span>