Moving within ruins (page 83): "Only certain troops are capable of clambering to the upper levels of ruins. Accordingly, only infantry, jump infantry, jetbikes, monstrous creatures and walkers may move on the upper levels of a ruin - and only if the model can physically be placed there. Other units may only move on the ground level of the ruin."
I play 'Nids. My favorite units are the Raveners and Homogaunts both of which are beasts as described in the 'Nid codex.
Well, my first game was against Democratus and his Chaos. He had placed all his beginning troops on the second floor of a ruin. It gave the humorous look of "woman on a chair afraid of mice".
Aside from that, I am a little peeved at this rule. I understand not wanting bikes on the upper floor of a ruin, but have GW not heard of "dismounting"? I mean, if the ruin is strong enough to hold a walker can 14 homogaunts be any heavier?
So far other than this little peeve, I like 5th-ed rules so far. Being the casual player the game does go faster and I like that I had a draw even with one of the better players of our group.
Now if Witch Hunters and 'Nids can get an updated Codex all will be well...