I was there this year (didn't go last year because the lineup wasn't that great for me). Mainly wanted to see Slipknot, Gojira (who fucking KILLED it) and In Flames on Day 1 and System, Deftones, Killswitch Engage (best set of the weekend) and Kataklysm (a closed 3rd place, behind KsE and Gojira). I did watch Cancer bats from the guardrail too, and I gotta give it to them for having a lot of energy. I felt they were very underrated throughout the weekend as no one seemed to talk about them going into or during the festival. I'm not a huge fan of their music, but they brought it live, especially their singer. Plus, I strangely enjoy their cover of Sabotage.
The mud made everything so much less enjoyable. The rain on day 1 was annoying, especially with the wind making it feel so fucking cold. The rain did come in handy though when it picked up really heavily during Gojira's set right when they started playing Flying Whales. I thought that was quite fitting. And then I got sunburned on my face on Sunday because i'm stupid and didn't put sunscreen on before heading in, or even during the show.
05/10 - Mastodon/Gojira
05/12 - Down
06/10 - DevilDriver