We have 1 XL (in the 25x80), 2 Alliances (the 20x80s), 1 Goliath (20x35) and one Spartan (HMSC 20x42). The XL is a fantastic unloader. A HUGE improvement over any of the other ones. I was about to swear off harvestores until we put that in because I hated the Goliath in the 25x80 so much. The XL unloads so fast... we had to get a new conveyor because the old one couldn't keep up. The Alliances work well on the 20 footers and we get the feed out quickly. Regular maintenance and adjustment is the key (which we do ourselves). All of our silos are empty at least once a year which makes it really easy to work on them. We use parts from our Harvestore dealer.
I'll have to look up what chains, hooks and such we are using. I know in the XL we had the hooks and paddles changed a few times right after installation (the company paid for it as we were the test farm for the unloader).