I have a set of four and have had the same experience as Matt. They are very strong and you run out of lift capacity before I could ever damage them. The pictures on the site show him lifting his backhoe! There are a couple things to be aware of:
One, notice the pictures on the BXpanded site. The forks attach at the top of the bucket, then drop down vertically past the bucket lip a few inches where they right angle out as forks. This means that when the forks are parallel to the ground as you slide them under the item to lift, your bucket is already curled down a ways.
If I'm using them to move piles of brush or to pile stuff up, the dump angle is somewhat limited by this. That is, when you dump your bucket fully the forks won't be anywhere near vertically down. I can usually just shake the bucket some and the brush will slide on off of the angled forks. If I've got the loader way up high to dump on a pile the forks can sometimes be too level at max dump angle and I may have to get off and shove the brush off, or just have a bit lower and wider pile.
The second thing is the quick attach. This is a pretty ingenious mechanism and the same used for the bucket hooks. You can very simply add forks, hooks, and reposition them across the bucket width as needed. However, I've found that, as mentioned above, the "W" pins do loosen up over time and must be readjusted.
These are the pins that go in the mount unit, then push down and snap in place. They put tension on the mount to the bucket lip and keep the mounts tight to the bucket. Over time the pins seem to loosen, or lose some tension, so you have to put them in a vise and tweak a little more bend back into them. I wrote to Harry at BXpanded and he sent an instruction page on the procedure to tweak the right bend back into them.
I've been pretty darn happy with all the stuff I've gotten from him. I have his forks, both type bucket hooks, trailer hitch, sprayer, carry all, backhoe and loader dollies. They've all been great for my uses!