I had a metal gitzo that came with spikes many many years ago--they were covered with a rubber thing that I just left in place. I don't recall ever using the spikes.
I have never used them but last month I wish that I had them, I was out near the ocean and the wind was blowing like crazy right into the lens hood on the 500 which made it like a sail
I am not sure spikes would have helped to plant the tripod into the grass but it wouldn't have hurt
My older Manfroto has feet which can be used as pads or you can screw the pads up to expose the spikes. I find the spike option not as useful as one would think. They slide on rock and just collect a lot of crud if used in mud, sand, or muck. My Gitzo has only the rubber feet and I have not missed the spikes.
The only time I have ever really wanted tripod spikes is going over the little wooden bridge at Ft. DeSoto's North Beach.....Some people just linger there
Nancy,
I love the spikes for turf and grass. The spikes help me cut through the soft stuff and get on a firm surface.
On boardwalks and rocky surfaces I prefer "Walking Cane Caps". The "Walking Cane Caps" help deaden some of the vibration transmitted through the boardwalk.
James