GameSpot has published their first designer diary for Titan Quest, with Iron Lore president and lead designer Brian Sullivan discussing the technology driving the RPG. He also adds a bit about what he feels makes the game fun:
The main objective we have tasked our gameplay designers with is finding out what makes an action RPG fun. Our first step was to get rid of a lot of things that are not fun, such as spending a lot of time traveling to and from town to sell your wares and micromanaging inventory, and instead focusing on the action and adventure elements that really drive action RPGs. We created flexible character classes and modifiable skills to let players really customize their characters to match their play style. To make the loot-collection part of the game even more exciting, we added a lot of unique equipment, each with hand-entered stats and art. And we kept the action and combat fast-paced and visceral, because that is what fans of this genre love about these games.