I've printed a lot of scrap plastic! But honestly, it's because I'm new to 3D printers. I haven't built anything huge yet, but I've really dialed down my small part accuracy! I work too much so I only have an hour or two a night max to play around with it, and that's when I feel ambitious.
I tried starting off with a large project, which was a mistake because I was still getting the hang of what I was doing. So I've shifted my project to my tiny multi-copter that I also got from KickStarter. My best version is in the link below. Green frame is mine, red is the stock frame. The pieces are small, so I can print most parts in 5-15 minutes, which is perfect for debugging and honing my skills. I'm pretty happy how the gMax performs now that I've calibrated it and sort of know what I'm doing. viewtopic.php?f=15&t=117
As for PLA sources, I'm still using the ColorFabb spool that was originally given to the KS backers. I haven't had any issues with it and I know the gMax crew speak highly of it. I bought a spool of Zen Toolworks Natural PLA from Amazon because it was cheap and getting decent reviews. I haven't tried it yet and hope it doesn't bite me in the ass for buying from Amazon.