I voted "Not sure", because on one end it was great and quite epic to ride around the old world and explore places a bit at a time, most recent example being the bamboo areas of Jade forest, and all those cool ground mounts that see little (if any) use, but on the other hand...
Wading through mobs to reach whatever item or mob you want to get at (The MoP Nesingwary-quests spring to mind, or EPL back in vanilla), the sometimes excessively circuitous paths you're forced along, or the areas that were designed for flying mounts outright that would need redesigning, i don't really want to think about too much of that...