Brief first impressions: I have the original Synapse and have used it for some 2-3 trips but never really warmed to its size/layout. For me once I filled the side pockets everything was so jammed in it was hard to find and remove contents. With the Synapse 25 there's extra room to move contents around to extract what I want. That allows me to use the outside pockets for everyday carry items so I no longer have to carry a Cafe Bag. My eyeglass cases are fairly bulky for example, and with the smaller Synapse there was never an optimal place for them, but with the 25 they fit in the outside side pockets without a problem. It's quite a large bag, of course, but so far it maintains its shape when partially filled better than my Smart Alec. I'm 6'2" and both bags are supremely comfortable to wear. Hope this helps those who are considering this bag.