they all sag, the shape bends depending on what you put in it. they are durable, wonderful bags with so much class.
the only ways i know to 'fight' sag are to use a purseket (purseketDOTcom) or to put a book (a reading book, large agenda, file folder of papers, a piece of cardboard cut to fit the bottom inside (no on would ever see it but you, and you would love the shape of your speedy again) be creative!)
Talking about the sag, if you arrange your things nicely in your bag the sag should be minimal. I once saw a lady with a super stiff, rectangular base and I do think that she's put a rather stiff cardboard in her bag. Uh-uh. Not attractive to me.
Yeah I love the sag. My mom's old Speedy 30 (from the late 80s) always had a bit of sag and it looked nice..it's not supposed to be a structured bag in the first place so IMO, it looks weird when it's made to look that way.
I do believe they changed the canvas to a thinner spun fabric coated canvas because i've purchased bags prior to 2006 and I prefer the 2005 and prior. It is thicker and it doesn't collapse or sag as much! I'm not quite sure when they did that but I've noticed the dramatic difference!