I think it is desirable but it could be dangerous also. Some investigators have shown a possible injury to endotelial cells. I prefere on-pump surgery when possible!
We used to use a humidified low pressure jet of air to expose the field, when necessary. I think this is safe as long as it doesn't damage the endothelium. It should be combined with judicious suction using a small sucker tip.
I have used CO2 blower since 11 years withot any problems and in 99% off-pump surgery in all surgical revascularizations. I think it is very effective and safe.