You're definitely not doing something right. Any and all PHP extensions I've tried thus far, whether it be something as "advanced" as eAccelerator or as easy as ionCube have worked as the install instructions have said.
I suppose something you might consider: Are you calling the full path to the extension? For example, my eAccelerator and Suhosin extensions are in the following directory, /php5/lib/php/extensions/ (that is root from my home directory) and I call the extension from within php.ini just by the full library name (ie. "suhosin.so" - quotes included). Notice that I'm not included the full path to the extension at all, just the name itself.
Outside of that I really can't imagine what else may be the cause of your problems. Apache however certainly doesn't need to be reset as it automatically re-loads your config changes.
I'd also like to address another point real quick while I'm at it. Autoconf is removed after php5 is installed successfully and therefore you need to re-compile it during the installation process of APC. In fact, installing APC is very similar to installing the Suhosin extension that I've documented in the wiki.
That said, I'll take the time this evening after class to document the install process of APC and I'll be sure to leave a link to it in this thread once it's finished
Hopefully that covers some of your concerns/questions for now, until the wiki article is done.
Chips N Cheese - Custom PHP installs and the like!