For what it's worth, I've been excavating a pond, sort of lagoon shaped 40'x20' on each leg. I'm in eastern Mass, which is glacial moraine country w/endless rocks of all sizes up to pretty good sized boulders.
I am about 80% done with the excavation, and it has taken about 8 tractor hours, using my B7900, and FEL w/toothbar.
A toothbar equiped FEL digs very effectively IMHO, except when you hit large boulders, and then some patience is required to pry them out. This past weekend, I "harvested" one that was 1.5'x2'x3'. Took about 10 minutes of removing overlay and around the front before I could pry it up.
For the size pond I am building, using the tractor and FEL makes perfectly good sense, particularly since I already have them and am not in much of a hurry anyways. (It's nice being outdoors on your tractor on a sunny fall day /forums/images/graemlins/grin.gif )
I'm planning to compact the bottom, cover with sand, let the whole thing settle over the winter, lay down a liner in the spring and then cover the liner with another thin layer of sand and flat landscaping stones to protect the liner from the claws of my dogs, one of whom intends to spend most of next summer swimming in it.
Good luck.