I can't comment directly on the Vertex but I use my ThinkTank Airport Acceleration in the same way. At the moment mine is loaded up for a wedding and it has got within it....
40D + mounted 17-55 with reversed hood
30D + mounted 70-200 f/2.8 IS with reversed hood
10-22 + mounted hood
50 f/1.8 and mounted rubber hood
17-85 and mounted hood
2 X 580EX, some eBay wireless triggers and Omnibounce modifiers
Pentax manual flash
Filters, batteries, bounce cards, ball bungees, toolkit, gaffer tape, portable HD storage/card reader
It can take a tripod - long or short - on the outside
I can even slip my 2 X flash brackets into the external laptop pouch.
It's a backpack but the straps do tidy away and the waist belt is removeable.
It's sized to meet most airline carry-on restrictions
I think in many ways it's similar to the Vertex in function/features but about $100 dearer. One thing I would say is that the suitability of a backpack like the Vertex or Airport Acceleration is dependent on the environment for use. For example, if I was using mine in the field, literally, with perhaps mud and damp grass under foot then there is no protection when putting the bag down. There is an all weather cover but that's not really the point. I've actually been thinking of getting a large shoulder bag, such as a Lowepro Commercial AW - something with a proper base for standing it down. The backpacks really need to be laid down and that puts the straps, or the bit of the pack that sits on your back, right in the muck. Of course, if you're just carting things to an indoor venue then no problem.
You can check out my early review of the Airport Acceleration here - https://photography-on-the.net/forum/showthread.php?t=393637 and see more pictures of it and a gazillion other bags here - http://www.taschenfreak.de/indexliste.htm