×Level 2
I think there's a little minunderstanding here. 1S 1E is a room with lots of brained roaches, located right to the east of room with tar mother, one goblin and 7 tar babies. The room where you keep removing roaches is
2S 1E, where I think many roaches/spiders/whatever adds challenge to the room and isn't frustrating. 1S 1E, however, has way too many brained roaches.
Oh, and 1S (room with tar mother, 1 goblin and 7 tar babies) has a backtracking issue. If I clear the room, spawn some tarbabies by stabbing a tar blob(without reentering!) and exit to the west or to the east, I'll be stuck(if I exit to the south, though, I'll be able to finish the level).
Level 5
1S: I have to lure serpent into dead end by myself now!
2S: Only one trap actually needs that escape covered by secret walls(one at 35,22-35,23). If you would remove secret wall escapes in other traps... this room would be cooler!
Bonus level
I like the idea of optional level!
Level 6
Entrance: Meh. I was quite tired of roach smiting, I have to say. But not frustrating, so I quite enjoyed this room anyway.
1E: I liked this room!
1S 1E, 2S 1E: Simple brained roach smiting rooms. there weren't too many roaches so I enjoyed these ones.
Level 7
Entrance: It could be more challenging if you would remove those arrows which surround Beethro when he starts the level.
1N: Nice tar smiting.
2N: I like rooms with lots of roach queens, even though they spawn lots of roaches.
1N 1W: Checkpoints were placed very well!
1W: if you intended northern tar blobs to spawn something, then you failed. tar babies don't spawn on force arrows.