I am running Cooper ST's on an 80 series cruiser and have done around 20,000kms now. I have to sya I do like them. They are noisier than the previous Kelly Safari AT's I had but it's not enough to anoy or bother me. I really have to say that I can't pick any difference in perfromance in sand compared to the Kelly's but they do the job well and are awesome on Gravel, wet bitumen and those wet dirt roads that get a coating of greasy mud a couple inches deep on them after the rain.
I like to run my tyres fairly low in pressuer around town but have had to pump them up to correct pressure due to a feathering at the edges. I have had no punctures and at the rate they are wearing I hope to get 50,000kms out of them.
I would recomend also trying to get a larger daimeter tyre than the std. This has an effect on spedo and low down power but is a great way to get a little more ground clearnace at the same time.