is it bad to tilt your pick towards the bridge when picking fast? is it a bad habit to get into?
As long as you get a nice clean contact with the strings and the sound you're after, then it shouldn't matter how you hold the pick. As most people here will tell you, it's all down to personal preference.
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As Hammy said, it's personal preference.

Shawn Lane tilted his hand backwards a good deal when playing extremely fast.

More often than not you'll see guys tilting their hands foward though.
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