Yes. It now only requires a level 30 character to ride a mount, assuming they've spent the gold required to learn the training to ride the mount, and to purchase one from a mount vendor.

Blizzard has offered the playerbase something new that can be used to level up VERY quickly. It is the Refer-A-Friend program. An active WoW player gives Blizzard the e-mail address of a friend who might be interested in playing. Blizzard offers them a free 10-Day Trial to try the game, during which, the 2 players accounts are linked together to receive triple experience (even with quest reward experience). The referred player may only level up to the 20th level with any one character during the 10-day free trial, and may NOT make a character of a race from the Burning Crusade expansion. Once the 10-day free trial is over, the referred player must purchase the retail version of the game to continue playing. All of his/her characters are allowed to reach level 60or 70 with the Burning Crusade expansion, or even level 80 if they purchase Wrath of the Lich King.

The 2 accounts are linked for 90 days, during which, so long as both players are playing characters within 5 level of each other and are within a certain range of each other (I believe it's roughly 40 yards in-game)  then they receive triple experience for everything accomplished. Quest Reward Experience, Mobs Slain Experience, etc, are all triple. This bonus experience does NOT use a player's Rested Experience either. The Bonus Experience stops for any given character at level 60, and for the accounts themselves once the 90 day link has expired.

Also, the linked players may summon each other to themselves such as a warlock might do with an entire party helping him.

Yes, the program will still be on your harddrive. If you go an extended period without playing and attempt to fire it up again (World of Warcraft) then you will have to download the most recent patch(es), on top of having to buy the retail version of the game, to be able to play again.

If no action is taken, then the game sits idly on  your harddrive, taking up room.

The answer is completely multi-faceted, and is dependant on so many things.

If you are looking to do a lot of PvP with this character, then your answer is probably going to be Undead, as Will of the Forsaken is such a huge pvp racial that it simply cannot be ignored.

If, however, you are looking for an entirely PvE perspective, then I believe that your answer is going to be dependant on what you are looking for in a character. I personally would say Troll because of the buffs that Berserking has received and would help you do more damage in a raid environment. Other races have quality points about them as well, so choose carefully.