This question came up a couple of weeks ago, and I think this is the info you want:
Robert, if you start with the magnetic lasso, click once and let go of the mouse button will give you the magnetic lasso. Alt-click and let up on the mouse button will give you the poly lasso. Alt-drag (hold down) will give you the regular lasso. Takes a little getting used to, but you can switch on the fly as you desire.
Chuck
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