Hi Derek,
What I really want is a REPL, or editor interface, that knows about Scheme so it can do parenthesis balancing and symbol lookup, and also talks with the reader so it can edit any line in a multiline S-exp currently being read, mark how much of an input line has been read if it contains more than one S-exp, put whole S-exps in the history instead of lines, and similar things.
Have you tried SchemeScript (http://schemeway.sf.net), a Scheme editor plugin for Ecilpse? It has almost everything SLIME&paredit have to offer (syntax highlighting, parenthesis matching, code completion, integration with the REPL, and much more), but not in Emacs (;-)
Dominique