I just won one of these at Irene. And since I cant quote that useless post that resarted this thread I thought I would actually add to it instead of stating that "yeah a grenade could come in handy."
Its no more heavy than the rubber grenades that we currently use. And I would only personally use it to clear rooms in a CQB situation and not in the field as yes, $50 is a waste to loose out in the grass. So with these stipulations I dont see that anyone could get hurt by one being tossed into a room, as long as you dont see someone and chuck it at them like a baseball. Which at that point, that person would have a serious problem and would be delt with severly.
For using this grenade to clear rooms I see it as being very effective. The report from the gas in the grenade alone is enough to alert anyone that a grenade went off. The problem with the rubber grenades is that they bounce quietly into a room and no one knows it was ever there untill some one trips on it. With the gas report, it should be easily reconizable and players are "notified" to look around for the grenade. In a room clearing you wouldnt even have to place bbs into it, just gas and it would notify the occupants that they are dead in the room that it is in. I would think it would be hard to miss. The bbs that fire out are only fired in on direction but are cool to add to the effect. I would not see that you would need to be hit by a bb to be out, since a real grenade in non-directional. Another plus is that it is a one time use, unless you carry gas out on the field. Also you can set a timer of sorts to have a 1-5 second delay after the spoon is released. The main body of the grenade feels and seems very durable.
Some negatives are that the spoon is not spring loaded and so after being tossed the spoon can come back down to rest on the plunger, effectively stopping the detonation "timmer". The spoon is also made of aluminum and I could see that if someone stepped on it, it would bend easily. The timmer mechanisim so far looks like it could be touchy and if you get it wrong you could possibly frag your self. I may add to this after I actually use it in a game.
EDIT: oh and someone stated that the bbs are spring propelled. That is incorrect, they are gas propelled.