I haven't looked at the Synergy but I've been using their Swiss Gear Maxxum for the last two years. This semester it's had up to 40lbs worth of books, notebooks, & laptop two days a week & lighter loads the other three and walking about a mile round trip to classes. The only change I'd make would be to add a waist belt.

Edit:
Letting all the compression straps loose will give you an extra two inches worth of capacity in an open topped pocket just the right size for text books.