I give little credence to those that complain so much about grenades or the launcher, particularly those dimwitted enough to add martyrdom to the mix. It's an ability that in effect plants a sign which says come stand by me and in 5 seconds you will be dead. Except for the few examples I discussed before, you have to be a crappy player that you get killed by standing next to the spot marked stand here so you can be killed.
That isn't the point. Everybody but everybody who plays the game knows to run away when they see the nade symbol or hear the sound. The point is that several of the maps are in highly enclosed spaces where getting away is sometimes difficult, either for space reasons or simply because chances are you just run onto a spot where another person has just died and inevitably dropped another grenade. If martydom doesn't frustrate you... I envy you. Drop in on the official CoD4 forums, you'll see that martydom, probably above even the noob tube, is the most complained about feature of the game.
And for other weapons being unbalanced/overpowered. If weapons existed as such, why wouldn't every player in a match be using them.
For several reasons.
1. Not everybody has access to them
2. Not everybody tries all the guns. Some just stick to their red dot carbine and never bother with the others, thus not realising how OP they are
3. Using OP guns just gets boring.
The latter was my own reason for stopping using the P90. If I use that gun then 99 times out of 100 I will dominate the game. Its just a guarantee of finishing top with an insane kill ratio. You can snipe accross maps with it and up close it is unbeatable. On some of the more open maps it can be tolerated, but on the more enclosed ones its just unstoppable. It was great while I was a lower level and was XP whoring because I wanted all the unlocks. Once I got them all it just got boring very very fast. I'd sooner pick up 15 kills in a round with a bolt action sniper rifle than 70 with the P90. Plus you answer your own question:
You see, that's the funny thing. I haven't used the launcher since I picked up mt first red dot site because of the limitations of it.
Once you realise that the nade launcher is good for a few quick kills but then leaves you stranded with a gun without a decent scope, you move on. It's a noob weapon - it gives you some quick guaranteed kills, but once you learn the game two or three kills isn't enough - you want to be on 10 kill streaks with your red dot or your AKOG. Doesnt change the fact that its frustrating as hell to get killed by one, because you know that its a one shot kill from medium range where pin point aim is not necessary. Like I said, its the CoD2 shotgun all over again.