There's a thread on Slashdot now about the MMOGlider case. I've never really looked at the software but I've heard of it. A lot of the discussion is leaning toward why people would want to use a program to play WoW for them and what that says about the game.
Someone suggested that Blizzard should look for a way to just completely remove the incentive for players to use it. If this program removes a hassle for the player then just remove the hassle from the game and the perceived need for glider goes away, therefore the program goes away. So the hassles here that people see in the game are time wasted running and the huge time investment in getting up to maximum level (70 now, 80 next month).
What follows comes mostly from my replies.
Blizzard is making changes that make it easier to get place to place but it takes time and effort. They've added a lot of new flight paths since I started (a couple years ago). They've added a couple teleport mechanics. In the new expansion (Wrath of the Lich King) they'll make travel to the new area easy from a major city. Apparently a side-effect of this will also make it easier for low-level characters to get from continent to continent.
As for travel speed they recently reduced the level requirement for mounts from 40 to 30. They also reduced experience requirements for getting from level 20 up to 60 (and with the next expansion they'll make 60 to 70 progression faster).
Balancing is still a trick though since people enjoy the challenges that come with leveling and one of those challenges is, oddly enough, organizing where to be in order to finish quests quickly. I enjoy questing and quest stacking is a bit of a skill that you develop from repeating quests with different characters and recognizing the patterns that Blizzard uses.
My main is a 70 mage and it took me about a year and a half to get there. Almost exclusively solo questing. I was mid-40s when Burning Crusade came out so I missed the rush while the rest of my guild was leveling for 70. I soloed my way up to 70. This time I guess I'll get in a lot more groups so the experience will probably be different than what I'm used to. I expect that early days on World of Warcraft probably saw a lot more grouping for world quests than we do now.
Looking at getting one of my other toons that range from 30-45 up to 70 seems like a lot of effort. That is to say, getting one up there fast feels like work. Leveling my druid is actually a lot of fun when I have the time for it. Thinking about how long it will be before she's 70 (or 80) is a little frustrating. I can't commit more than one or two nights in the average week to playing a game and even that really is a lot of time.
Overall Blizzard's done pretty well with balance for questing in the world as far as I see it. Some classes are easier to solo with than others and that should influence what class someone wants to play. Diversity and balance are two different things. As long as those characters with a hard time in some circumstances have an equal occasion for perform well then those aspects of the game are balanced.