Ya, I hear that there is a lot of content in Runecape, especially for premium users, and they send out updates just about every week. If you like the sort of game that runs in a browser on Windows, Mac, and Linux with a persistant world to explore, very few games can stand up to this one.
Level up on Free Worlds until you are at least 40 combat, then if you still enjoy it then upgrade to members. There are alot more quests, content and nice armour and weapons that are only available on members worlds. I have been playing RS for over five years and I am never bored.