I have a Rover AW2. Used it every day for a 5 week trip around Europe and didn't have a problem at all with the bottom opening up.
Just make sure you do the zips up properly and use the quick release strap as back up. It fits quite a lot of camera equipment. I had no problem fitting in a 1D, 24-70mm, 580EX and 70-200mm f4 plus other bits and pieces including a manfrotto digital tripod.
Side pockets are good for water bottles and lens filters. The top part isn't that big though as the shape is quite tapered. A jumper, some maps and food and it would be full. I found the bag to be comfortable for me to wear all day which was impressive as it would weigh around 9-10kg with water bottle.
Also I found the tripod carrier was good for large tripods, but if you have a smaller tripod I found it easier just to hook that into the elastic straps instead of folding out the tripod holder. (But then you need to be careful to put the zips for the top compartment on the sides otherwise the weight of the tripod can open the top compartment)
On the negative side, it is a pain to get your camera out from behind so I ended up walking around with my camera around my neck for most of the time so I wouldn't miss anything. And although I was not particularly careful with my bag, I was a bit disappointed with the level of wear on the bottom of the bag when I got home. It is not like a hole will form soon, but the scuff marks stand out quite a bit.
Hope this helps.
Aaron