With the advent of EoC, many things have changed. One thing in particular caught my attention, and it's the way combat XP is gained when killing a monster. Now instead of getting XP per hit, you get XP per kill, so basically, it's like RSC, where you gain XP per kill, rather than per hit. If you don't know what I'm talking about, click on the spoiler and watch the video.
Another strange thing I've noticed is that Jagex can do a rework of something (be that NPCs to towns and dungeons), and STILL leave certain areas untouched.
Example: The dwarves have had their chatheads updated, yet their NPC sprites are still the ones they've had since RS2 was first launched.