Personally, one of the reasons I think the beta is such a good thing isn't just because it's a huge update that needs tons of testing, it's also because the player base can learn the system. They can figure out what items are good and bad, how exactly abilities work, what they want to get before the beta goes live, what new items to get once it's live and how to get them. Not to mention come up with new boss strategies, new slayer strategies, etc, etc. Basically, by playing in the beta you can acclimatize yourself to the new system so you know what's what when the live update comes. Now that I think about it, I think a f2p beta might be a good idea when it's closer to coming out...