I find the gallops very useful. They improve your horses fitness for a start, but more than that they give a good indication of how a horse likes to race, eg handy, hold up etc. And of course you get a good idea of their 'level', how they compare with others in your stable so you know what type of races to enter them in (especially good for untried 2 year olds). Also to get them used to all weather.
I've got a feeling they do help improve speed/stamina/jumping over time as well, depending on type of gallops undertaken obviously. I strongly recommend regular gallops
