I understand that errors don't tell the whole story; they are also not irrelevant. When you look at the defensive value of a player (or his offensive value as well) its important to use all of the data available. There are those who think that UZR is a good way to look at value defensively. Maybe it is. However, the sheer number of errors committed is hard to get around. Personally, I think that overall he has been a pleasant surprise. His defense is likely to improve over the course of the season, based on his history. As things stand right now, the errors stick out like a sore thumb.
The ground ball lost in the lights and the linebacker type treatment of his colleagues were freak events...somewhat humorous except for the fact that Ellsbury is still not healthy.