Didn't get very far, in .55a the first brown door was bugged (made sound but didn't move) and in .55d the debug door at the beginning works but the entrance door is still bugged. Other than that the new pistol is nice and feels punchier, even if I miss the glock.
EDIT: Went back with F having the doors fixed. Flow of the level is nice never really got lost even in the more open areas despite most of the area looking similarly grey. The new pistols are definitely really good, especially when dual wielded, as I went back to them consistently even when I had ammo for other guns. The harpoon chainsaw is a fun addition. The leggy guys felt like they had more reach than they should and hit earlier than their animation would suggest.