Regarding zoom creep... there's virtually none.
If you simply point the camera directly down, it does not move.
If you point the camera directly down and change the focal length, it does not shift from where you put it.
However, if you point the camera directly down and start vigorously shaking it up and down, it'll creep a bit
Now, regarding the feel of the focus ring... i rarely use it since the AF is faster than i'll ever be
However, i can say that it's a bit stiff - probably from it's unusual design. As I mentioned before, the focusing ring is free-spinning and can be rotated as much as you want - and while moving the focus ring will change focus, the camera changing focus wont move the focus ring. And probably because of it's construction, the ring itself doesn't spin too easily compared to the quickshift on the kit 18-55mm lens for example.
Despite that, it's not too stiff to be a hinderance, it feels like it can still be finely tuned to how you want it.
One amusing thing to do is to set the camera on AF.C, half-press the shutter and keep spinning the focus ring.. heh
In other things.. here's a photo I took today with the lens @ 135mm
Above image is downsized...
Click here for the even bigger one
When the photo is cake, who cares about distortion