If something's got you feeling ate up, then you might be consumed by the notion that it didn't go perfectly. You're overwhelmed, obsessed, or maybe you're just exhausted. However, among members of the Air Force, ate up has long meant gung ho. This is part of a complete episode.
For consumed/focused/obsessed, I'd personally prefer "eaten up"…
The Army usage of the term is not at all complimentary. To soldiers, it describes a person (or command structure) that is willfully incompetent and/or disorganized. Overwhelmed? Maybe…but by routine tasks that should NOT be overwhelming, to merit this description. The term can also be applied to situations or circumstances, analagous to (but not quite as extreme as) "FUBAR". The closest it comes to Grant's umbrella definition of "consuming/focused" (and this is a real stretch!) would be in the sense of "waste of time", possibly from a sentence like "the brass ate up our whole day with make-work, then made us put it all back the way it was!" being reduced to the shorthand form of "today was totally ate-up!" or "this company is ate-up".
Most recently, the term was particularily applied to (and within) the former 8th Infantry Division, whose symbol is the number eight bisected by an upward arrow (hence "eight-up"), which in the last few years of its existence (it was "drawn down" in 1992) reputedly was poorly run, badly prepared, had obsolete broken-down equipment, low morale, etc. This may be why the negative definition is more recent, and hasn't gotten much traction (with the eponymous unit no longer active).
One unusual usage I personally overheard was a country-born sergeant dressing down a recruit with the statement "Pac-man done ate up yo' brains with stupidity!", but I have no idea where that man hailed from. Hmmmm, Pac-man… ('< – – – -
This brings to my mind something purely personal. When I was in college, in the sixties, my friends and I would frequently ski out of Ruidoso, New Mexico. At that time, low priced motel rooms went for about 20.00 a night and of course that's what we tried to get. There was, however, one place that had many signs nailed to trees by the road that said, "Rooms – $8 up." Every time we went by one of those signs the comment was made, "If you stay there you'll come away ate up."