It was clear for a while that the atlantis crew wanted to do a horror type episode. After watching this, they got the atmosphere right but missed the jolt (fright) factor by using predictable cues way too often. Apart from Vega's death, Will Waring, the director built up the scene well but failed to utilise it.
The creature effects were very nice but not really scary. The use of fog in my opinion was a bit of a cheap shot to create tension. However I do give full marks for the fact that they decided to have a go and gave it their all.
Hopefully this little stumble isn't the beggining of a trail of mundane filler episodes, (Next weeks ep: The Queen could be really good or really bad.)