Your picking more with your thumb and finger than you are with your wrists. That can be holding you back. At slow speeds, its not biggie, I do that for better accuracy and combined with your wrist, can sound powerful, but for fast picking, you need to keep them still (without making them tense) and use your wrist to pick while you change strings with your forarm/elbow.

Nightlifter: IF your using your thumb and three fingers to grib the pick, it seems like that would put the pick at an awkward angle and make your wrist compensate for it, making it harder to pick fast and effeintly. Try only using your thumb and index. If your having trouble with the pick slipping away, its normal and you'll work through it. I know I resituate my pick while playing, but you never notice since it comes natural, like breathing, you just do it.