I think mine is about 65 pounds. It's a bubba keg however which is the predecessor to the BSK.
It also comes with a really nice cast iron grate that can sit closer or further from the fire depending on what you need as well as a swivel grate on top that works very very well for such a simple design (perhaps my favorite feature about the whole grill). Additionally, it comes with a better gasket...at least better than the one's offered on the eggs 2 years ago. I'm not sure what BGE is offering now.
It's also more efficient than the eggs but that's has it's good and bad points. You can touch the outside when it's 700 degrees on the inside and it won't burn you and it uses less charcoal, but the downside to that is it is REALLY hard to bring the temperature down if you overshoot the target temp because it does not diffuse heat well. Mine cools off at a rate of about 1 degree per minute...so you could see how that could get annoying if I over shoot by just 50 degrees.
I agree with everybody else though. The biggest advantage is portability. Sits on a hitch if you need to take it somewhere but also works great for moving around the house. It's not just "on wheels", the cart is pretty much a furniture dolly and you can drag the sucker across the yard with no issues whatsoever. I keep mine on the patio when I'm cooking and then move it around behind the house when I'm done just because its easy to do and makes the patio look less cluttered.