I like whippets, they are great little dogs, and a great the turn of speed and gut's.
A lot of what has been said above though rings true to what i have experienced, i work twice a week, all day, in the dales during the season. I've seen collie greys we have bred from 3 generations of collie greys not make the grade, and carried off dogs with broken legs, smashed up feet, with the wobbles.
We have had whippets as well, and witnessed one drop dead due to the workload on it's heart up there.
The old guy's bred the crosses for a reason, just like there fathers did, and just like i will do. The