That's because when you skip it uses a retail key (i think?) so it shows you the metro activation alerts. Volume channel only puts the little watermark in the lower right.
How usable is this? I'm thinking of installing it and using it un-activated until I get my key in a few days. That nag screen, how often does it popup?
does the enterprise iso allow installs of core or pro in addition to enterprise, using the ei.cfg file ?