The Eagle A-III is a great pack. I have one and I also have the Blackhawk vesion. Yes it is plenty big enough to hold enough for a three day hike but you may find it lacking in the comfort department as it has no frame. I believe eagle sells an insert that acts as an internal fram of sorts. In any case they are great packs that are virtually indestructible. If you're going to buy one shop around. I've seen the prices vary from $80-$130.

Brian