Non-obvious features:

Command-return and keypad-enter, as well as command-e, are keyboard equivalents for evaluate.

Tab adjusts the indentation of the line the caret is on, or of each line included in the selection if there is one.  The ``adjust indents'' menu item does the same if there is a selection, but adjusts the
entire window if there isn't one.

Evaluate with no selection tries to find the top-level form the caret is on, using the convention that top-level forms should start in column one, with no other lines starting in column one.

Quadruple click selects a top level form, as above.

Double click on a parenthesis, bracket, or brace selects the parenthesized list, rather than a word.

Holding down the Alternate key while typing return inverts the autoindent preference (i.e., gives an non-indenting return if autoindent is on or an indenting return if autoindent is off).

All input to scheme needs to be explicitly sent with ``evaluate'' (or equivalent), even if it isn't an evaluation per se.

Left_Alternate-Control-Esc kills the scheme process and starts it again.  This is useful, for instance, after changing the scheme dialect preferences or command-line options.