Ah, I'm looking at this out of context. So making this hurt you won't necessarily result in an increase in difficulty, and if it does you can decrease the difficulty of other things.
Difficulty increases because the player has to pay attention not to step on those areas, whereas before he could just rely on the fact that the character would automatically slide along the edges, as if against a wall.
As for making some other aspect easier, that's something I wouldn't touch both because I like the current balancement and because the missions have been designed keeping such balancement into account.
How awkward is it to navigate around the edge these rooms?
The controls themselves are very simple (left/right to rotate, up to run forwards, down to walk backwards) and responsive, so controlling the character is easy in general (if you want, you can try yourself with the demo
What has most importance is the layout of those areas... mmm, now that I think of it, the current missions aren't particularly problematic in that sense and the tiling engine is such that there's always a good deal of room for movement - f.ex., consider this other picture:
the acid pools are dangerous, but there are always at least 16 pixels of safe room (look at the sides close to the pipes).
Mmm... maybe I'm just being overly cautious
Will enemies try to pull you in to the centres?
Good question. Simple answer: no