Here is a small but significant change to a piece of equipment between DF and the DFRPG:
The Dwarven Whetstone in DF1 "Gives edged weapons +1 damage for sharpness with first blow that connects after sharpening".
The same item in DFRPG's Adventurers "Gives cutting or impaling weapons +1 damage for sharpness with frst blow that connects after sharpening".
We'd read, and played, the first one as specifically working on edged weapons - and thus, cutting attacks. Not impaling.
The second is a big change from how we'd played.
I'm curious if what is in DFRPG was intended all along, or it's an expansion to allow "first stab" benefits for otherwise weak impaling attacks.
One thing it's changed right away is that suddenly impaling arrows do +1 damage (sharpen them all before you enter the dungeon.) That's a significant difference - a Scout might be doing 1d+3 (2) pi with a bodkin but 1d+4 imp with a broadhead - and if your opponent is 0 DR, that's 3 injury to the vitals you gave up with the otherwise standard-use bodkin. Cornucopia quivers are nice, but produce arrows that do one point less damage than your store-bought (or homemade) impaling arrows. It's a noticeable wording difference, with a real game difference.