And if you decide you need to go back to an early zone to get low level minerals or herbs? Instead of meekly wandering around ignoring you to gather in peace, now the local mobs are the same as you again and aggro on you. So you have to fight your way in and out. Same spell rotation, over and over and over. 31373433. 31373433. 31373433. 31373433. 31373433. 31373433. Every combat the same. Over and over again. Never ending. No change. Mind numbing. No challenge.
By constantly doing quests, you will experience a very different game than if you just level through pure grinding. You'll be out there making a contribution towards the Alliance or the Horde. Doing these quests takes you through the heart of the game's story AND provides the fastest rate of experience. Have fun in World of Warcraft and enjoy developing your hero - your adventures will gain you great reputation amongst the land.
The neutral auction house can become one of your best friends. Other players are constantly checking both factions' auction houses to find an appropriate price for the good they demand. Often times, goods are cheaper on the alliance because they have more people, thus, the supply increases as demand decreases and price goes down. If you are horde, feel free to transfer gold to your alliance toon through the neutral auction house in order to buy them item and bring it back to the horde side where it is more expensive. The 15%, as of patch 3.3.3 (down from 30%) is well worth the extra 50% or more you can easily make on one item alone. Blizzard decreased the neutral cut for a reason to 15%, that reason is to get trade facilitated between the horde and alliance. Make sure you take advantage of this! Tips when trading between factions: