> So you are saying this is good style? And how is this supposed to offer
> the option that people like me don't want to have the keybinding without
> setting it explicitly in .emacs.
If it's a keybind on a specific mode, and if it doesn't conflict with the keys for that mode, then it's low-impact enough that it's alright.
It's safe to assume that a user who installs SLIME would like a convenient way to start SLIME from lisp-mode. The cases where that's not true are unlikely to be bothered by an extra keybind. The cases that are bothered (because it conflicts with some personal keybind), will have to add a line to their init file (either to prevent activation of your package or to fix the conflict).