I had read about this and, at the time, I had no interest at all. A couple of years ago I played LOTRO for a while (like DDO, a Turbine game), and while I had quite a lot of fun, eventually I grew bored of the repetitious grinding, and mindless killing. So, when a friend started trying to talk me into trying DDO I was highly sceptical and took a fair amount of convincing.
Finally, just to shut him up, I decided to bite the bullet and download the client...
I have to concede, I'm significantly more impressed than I had ever expected to be. It actually does evoke a D&D feel, there are puzzles, and grinding is far less at the forefront than LOTRO.
Also, while fun, it's not terminally addictive, and it's very casual friendly. Dungeons vary in length and you are informed up front roughly how long the instance will last. This means if you only have an hour or two, you can easily complete a couple of instances and then log out.
Anyway, the reason I created this thread is just to make mention of it to people who aren't already aware that DDO is a surprisingly decent game; it requires a certain amount of intelligence and appreciation for more traditional D&D-based games.
Not only that, while you can spend money if you want to, the core game is free to play, so the price is right.