I don't own one and haven't shot one, doesn't prevent me from adding my .02 though.

The consensus is that they have more felt recoil. But certainly not shooting gas, unburnt powder etc. directly into the action is a good idea.

For a soldier or someone else that needs absolute reliability in adverse conditions it is certainly something to look at.

For a guy like me that shoots for fun and competition I know that my properly built ARs will run fine with just a little bit of maintenance.