I started the 500 piece Springbok Wacky puzzle during the night last night, and just finished it. Took me about 6 hours to complete. The pieces are pretty big, and it wasn't very hard; not sure why they classified it as an adult level puzzle.
I have a Jaymar puzzle without a box that I got in a trade years ago. Think I'll try that next, to verify that all of the pieces are there. If they are, maybe I'll pass it along.