I recently acquired a 17mm f4 lens for Canon FD system.
My widest lens for 35mm thus far has been 28mm.
I went for a walk in the local nature area and I must say, shooting with a 17mm is a totally different experience.
I instinctively spin the focus ring looking for the image to blur and sharpen. But a half turn of the ring makes almost no difference. Everything just seems to be in focus from about 5 feet on. So a certain amount of 'trust' that the exposed image will turn out sharp is required.
Also, to get any person-sized object to appear prominently in the image, you must get close.. really close. About 3 feet or less than 1 meter seems to be about right. For smaller objects you need to be damn near on top of them. Remembering to get close enough to objects can be a burden. We have a tendency to shoot from a safe distance and if you do so, most things will just be too small in the final image.
Another issue I have is the sky. Around here the sky is rarely interesting. It is a gaping hole in the artistic sense and burning pan in the exposure sense.
I really like the way the 17mm works with trees. With other lenses, its is a rare occasion that you have enough room to get the whole tree in frame. And the perspective works well as it can accentuate the size of the trunk, especially nice with massive oaks. Another nice thing about it is that you can single out one tree, its neighbors quickly diminish in size.