I sunk quite a few hours into Silk Road, and I'm not ashamed a bit of money into it too. It's a fun little distraction from WoW, and it is free, or at least used to be. The best part about it, is that it's peaceful, nobody telling you how bad you suck, even if you feel it. You can solo a lot of the content, and it's not that hard to find other players. However, that means there is stiff competition for mobs, unlike in wow where it's mostly quest based.
Fun, good little time sink, but still not worth investing too much time in (though it is eye candy)