The bearcharge helpfile is less detailed than the bash helpfile, leaving me with a few questions. Does weight affect the success/failure of a ranger's bearcharge? Is it less likely to succeed against a much smaller foe? Is it harder to bearcharge a target that is already directly fighting someone else, particularly someone large? Basically, does it have any or all of the same success/failure modifiers as bash?

Smaller targets are better for bearcharge. In this sense it's different from bash -- bash, you ideally want to be 1 size bigger, but 2 sizes and you can't bash. Bearcharge, bigger is always better.

I imagine the ganging-style difficulty mods are pretty similar with bearcharge vs. bash.

Weight I'm not sure about, but my rangers never whored out weight and my impression is that bearcharge is a lot better than most rangers seem to think it is, so I'm guessing it either doesn't matter or it doesn't matter an enormous amount.

Thanks, nepenthe. As for anti-ganging modifiers, I found a post by Sebeok that seems to answer that, in case anyone else was wondering:
"Bearcharge hasn't been changed other than the same sort of antigang stuff like bash,trip,etc have"

like this instead of your usual vague and ambiguous answers. Im guessing most people like that too.
You really should keep that up.