It's big and heavy. I was really quite shocked at just how big and heavy. Somehow the weight and dimensions quoted (which are accurate) don't seem to do the thing justice once it's in your hands. The size means you won't be able to use the viewfinder or flash, and the weight makes the camera awkward to hold. You need to bear in mind that the lens is mounted on an adapter which is attached to the camera, so the additional weight of the lens is offset from the body and it does feel weird and unbalanced and I ended up holding the thing more like I would an SLR but using the LCD for framing.
Getting it attached to the camera isn't difficult, remove the sliver ring at the front and clip in the adapter. The lens screws into the adapter. I've left the lens attached to the adapter so there's just that one thing to do.
There's a *lot* of glass in this lens. There's no way to add a protective filter at the front so you have to be extremely careful not to get fingers onto it during use. Dust is also going to be an issue, though a good blast of air from a rocket blower sorts that out.
That said, it does the job and returns good images at ~24mm focal length and up. 24mm is a lot better than 35mm and you'll get a lot more in your landscape photographs. The camera main lens continues to zoom when the adapter is fitted, so you're not stuck with a fixed 24mm focal length.
The lens comes with a pretty good pouch to hold the lens and snug fitting caps for both ends. It's probably going to spend most of its time in a drawer, only coming out when there's going to be trip where it's sure to be used.
In summary, big, heavy, expensive but effective, 3 stars just on practicality grounds, not performance.
Please Canon, make your follow up to the G9 have a minimum focal length of 28mm.