Though I don't have the capability to use an e-boarding pass, even if I did, I would stick with the paper one, partly for the reasons you stated. But also partly because I need the boarding pass to access the NW lounge (AmEx Platinum card). And what happens if/when NW doesn't credit miles? Do you send in your handheld device in order to get credit since they want a copy of your boarding pass?!
Though I enjoy the convenience of technology, this option is mostly designed for computer geeks to get their fix
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I know someone (IT-related) that is an NW employee and works in this area. He would find your last sentence quite humorous
Truth is, NW is rolling this out at MSP as a test to see if the public will use it, what the uptake is, how the equipment performs, what the reaction is, etc. If it succeeds - no telling what the measures of success are, though - the plan is to use it to justify removing some of the kiosks, first at MSP, eventually system-wide.
There are no decisions at DL+NW these days which are not related to cutting costs long-term. This is one of them.