I assume it expends the scroll in the attempt. I would be willing to accept that process happily in most cases (and I suggest the same for Clerics learning new spells!). However, I am leery about the Artificer's spontaneous access to all spells. How about this--we use the by-the-book process for Artificers in learning new infusions, but we only let them have spontaneous access to a number of infusions equal to the number in the Eberron book. So each day, they can swap out any number of infusions from the regular Eberron book for any number of new infusions known, and vice versa, but never in greater number than they started with. This is still quite powerful--it's tantamount to a Sorcerer who swap out her spells known each day, but I'm much more comfortable with that. Does that sound good?
