I think the main thing that makes them not too practical is the fact that they are wide open, and can't really be enclosed to hold in heat at all. This makes them awesome for their intended purpose, but pretty challenging for other types of cooking. Grilling is the main thing you can do.
With that said, if you've got the $$ and you already have other types of cookers (smokers, etc.), they are pretty damn neat. Very practical for grilling and entertaining. Not really practical for mulit-function use.
Sort of like one of these: