There are two obvious problems... (1) if a researcher submits an electronic request from home or the office the day before planning their research trip and then never shows-up, the staff has wasted their time performing the pull, and the record remains unavailable to other researchers for a period of days; and (2) the electronic finding aides, including ARC and its successors, are not yet complete enough to enable identification of box level items without intervention of an archivist or technician.
There are probably many more questions and issues that need to be addressed. NARA staff will be holding a public meeting on this subject (this schedule is probably tentative) :
The meeting dates are:
Archives 1,Room G-24
Archives 2Lecture Room B
Come to the meeting. However, if you can't be present you should post comments and questions here, and on the NARAtions blog on other issues relevant to record-requests that you would like to have addressed.