However, my main excitement is because the expansion has the mandate to fix some of the big issues that World of Warcraft currently has. Of course we have all sorts of cool updates coming, like new races, professions, level cap, etc. but still for me, the other changes, specifically to older content, are more important.
First and foremost, Azeroth, the old zones of vanilla WoW are getting a thorough make over. Why is this such good news? Because the old content is hopelessly out of date. There is no saving it and is one of the most painful things to play through. Sadly, it still represents of 48% of the game's content. Not to mention, simply the content that we spend most of our time leveling through.
Dungeons design, quest organization, gear drops are all things that continue to plague this part of the content, making it unappealing and dry. So much has changed and Blizzard's design team itself has grown since those times that makes looking at Northrend and vanilla like day and night. But no more. We are getting two new races, starting to zones, new zones, and the old areas are updated. Awesome, is what I say.
Second most wanted on my list is a revamp of the character stats, a subject that keeps hindering the game a lot. Simply put, it is just too complicated. Aside from hardcore players, most do not know, or even want to spend hours calculating. Yes, looking at new gear, checking and planning how to get the best results has its appeal and is part of the fun but also distracts you from the game itself.
Especially, when you have to judge items on the fly, with less time to make up your mind than you would reserve for peeing. This is immanent on a lot of raid loot, where e.g. a weapon might drop, that has a lot less attack power than your current weapon, but than again it has useful stats like expertise and armor penetration on it, so is it actually better or not?
This is all going to get streamlined in Cataclysm and I for one, will be happy to see them go.
Spell Power: Will be removed and instead, intellect will provide both mana and SP at the same time. Just makes you wonder why the game did not work this way to begin with.
MP5: Will also be removed and replaced by spirit. To compensate, healers will also gain a meditation-like ability to help them regain mana more efficiently.
Armor Penetration: Aye, this one is on the boot-list and I am happy to see it go. Looking at the ArP history, it either never worked, was over-powered, or just downright confusing. Rest in peace.
Defense: Is going to be replaced by talents that provide tanks with the uncrittable status. It, essentially, is not a confusing stat, up until you begin to wonder how much benefit you are truly getting from stacking more than the necessary cap limit. All around better though, will make gearing for tanking a lot easier.
Attack Power: The same way as SP, this is going to be removed and replaced by agility and strength, for leather/mail and plate wearers respectively.
In general, more weight is shifting to emphasize the importance of the basic stats, like intellect, strength, etc. While currently, the two different groups of stats are locked in a struggle for dominance. It will be clearer and simpler in my opinion. A much desired change.
There are a myriad of changes to the game in cataclysm. Too many to be listed here. For more information, I would starts with the official site, and work your way through wow.com and the mmo-champion.