I got this for my last trip:
http://www.bhphotovideo.com/c/product/672935-REG/Lowepro_LP36144_PEU_Pro_Runner_350_AW.html
It's a LowePro Pro Runner 350 AW Backpack.
Fits D-SLR Camera, 4-5 Lens Kit
Holds Notebook with Screen up to 15.4"
Weather-resistant 600D Ripstop PU
Padded Interior
Padded Inserts and Adjustable Dividers
All Weather AW Cover and Rain Flaps
Hideaway Tripod Mount
SlipLock Attachment Loops
Exterior and Interior Pockets
Backpack Harness
I carried two camera bodies, (D90, D60), a SB700 flash and a Tokina 11-16, a Nikon 18-105, a 10.5 Nikon fish and a Nodal ninja pano rig to the parks. I also fit in a slot for my 2 filters and assorted lens cleaning crap. The tripod mounted beautifully on the outside with enough straps (3 plus a tripod foot support cup type thing that strapped on the back below the bottom of the bag)... so that the tripod was not a PIA and wobbling around.
I didn't carry a lap top in the sleeve but I did stuff my cotton carrier harness in there so that was super! The side pocket only holds a small H20 bottle and that's my only beef with the bag. Carrying around all this stuff is heavy but the bag does come with a padded waist belt that you can use. If you don't want to use it you can stuff it back into it's pouch like area.
Carrying all this crap around was heavy so when I did want my full gear selection with me in the parks (Like on One More Disney Day) I checked it in at the Lockers at the front of the parks and they kept it in a closet for me, which was GREAT! (I could go to the lockers repeatedly and they would bring out my bag and then put it back in storage until I needed it again, all for the low price of approx. $7 bucks!)
I could see walking around for awhile with this thing loaded, especially if I used the waist belt. It wouldn't be "Fun" but if it meant not taking the stuff I wanted, I definitely would pack it any way and just deal with the weight because the bag has the waist belt to help distribute the heavier loads.
Last week I was schlepping this bag back and forth to NYC on the train with my D90, 18-105, filters and some pathology slides and medical records. I took out the velcro dividers and rearranged them to pack
that configuration. The bag is still heavy because of all that it was carrying but I didn't feel like it was too enormous or bulky. Then again I take great joy in whacking people with my camera back pack so that is an added bonus.

Think of all the extra personal space you will gain for yourself in crowded areas when you are 'rockin this beast!
The bag is solid and well built with plenty of padding so I don't worry about normal use like stuffing it on the floor of the train seat.
I also have the Pro Runner 450 AW Backpack which I use for storage and transport. Talk about a beast, this model is HUGE and Heavy!! It's great for keeping "all that" in there but it was a little too much for me to schlep around to the parks and elsewhere. It is a place to put things like lenses I'm not using and all the other camera ephemera like cords and chargers.
So there ya go. Personally I feel you can't go wrong with lowepro. The bags take a licking and keep on ticking and the zippers are great.
I ordered two bags from B&H to compare before my trip, the LOWEPRO 300 and the Lowepro 350. I wound up going with the 350 because I could stash my cotton carrier in the lap top sleeve. The 300 has the same size interior as the 350 but does not have the lap top sleeve.
B&H has a great return policy so no worries there.... I sent the 300 back in 2 days with zero problems from B&H.
Hope that helps...
~Joanie