After trading in my ample collection of Olympus gear, I'm starting from scratch. I don't have everything I need yet, but the 7x has room for it when it comes. So far in the bag:
• Canon 6D with Canon battery grip
• EF 17-40mm f/4 L USM
• EF 50mm f/1.4 USM
• EF 300mm f/4L IS USM
• EF 100mm f/2.8L IS USM Macro
• Peleng 8mm f/3.5 circular fisheye
• Full size speedlight
• Macro ring flash (not an LED ring light... those are a waste of money)
• Extension tube set
• Off camera TTL cable
• Cable release/Intervalometer
• Spare camera and flash batteries
• Lens cleaning stuff
• Headlamp
• Hiking towel
• Probably more I'm forgetting, like tripod tools, etc.
When I get the 70-200 f/2.8L, the ring flash will have to lose its case and live in the laptop pocket. A second 580EX type speedlight will stack over the current flash, and there is still a ton of room for wireless triggers, filters, etc.
The backpack is also an excellent place for all my gear even when it's just chilling at home. I don't baby my gear, but I do what I can to keep from breaking it, and so far the Tamrac has done the job beautifully.