I have the DSLR Video Fastpack 350 (
DSLR Video Fastpack 350 AW Camera bags, backpacks and rolling cases) and find it very comfortable with the straps. It has plenty of room and when I bought it, it needed to have room for a 15.6" laptop which this one has. Here's an example list of what it can carry, have in mind I don't own everything on this list but it will easily fit (for example grip and several lenses mentioned below):
Camera compartment
DSLR with grip and 16-50 mm attached
70-200 mm
100 mm
Flash with diffuser
Cables for laptop
One of those rocket bellows
Top compartment
Two pairs of underwear, shirts and socks
Book or small bag for toothbrush etc
Special case for small cables included in backpack
Pens, batteries etc in inner compartment
Rear compartment
15.6" laptop
Magazine
Hidden rear compartment
Some extra cash
Passport
Outer holder
Medium sized tripod, for example Manfrotto 190XPROB or a water bottle
I've actually walked with this pack filled with nearly this much in it, apart from the tripod and even then it's pretty heavy but if you have to, you have to.
I don't do any weekend business trips but I could imagine that it might work if you want to mix some pleasure in the business trip