In reply to 'Hilda':
I have the old A50.
I find it more comfortable to carry without the frame.
It is very light and very tough. It has become quite tatty-looking, but there are no signs of wear despite some serious abuse.
I like its big size, light weight, sturdy cary handle for hauling, top compression strap, large side compression straps (ideal for sleeping mat, shovel handle, tent poles, etc).
I dislike the way the rear lid adjustment straps flick me in the face on a very windy day.