Problem with the rock-it launcher is that the ammo has weight. Also, picking shit up and loading it into the gun is fucking tedious. Overall, i was REALLY underwhelmed with the heavy weapons selection in this game - the Gatling gun comes way too early and is pretty terrible considering how fast it goes through ammo. Even with completely maxed heavy weapons skill it took me 50+ bullets to kill a super mutant. And with how hard money is to come by in this game, I think it's kind of ridiculous. The fat man is great but there's no ammo and using it feels like cheating against everything but the enemy it was designed to kill. (I'm not going to bother spoiling it, you either know what I'm referring to or you don't.) The only heavy weapon that really turned out to be worth the investment was the gatling laser, but it takes entirely too much work to get unless you want to go around the countryside whacking exiles all day. (By the way, I'd be willing to bet that the entire reason that you can find the brotherhood exiles wandering the countryside was all the bullshit comments people were making about bandits wearing power armor. You have to hand it to them, they at least have a sense of humor about their criticism.)
Energy weapons are retardedly good, small guns are nice for stealth characters. If you care to spend a ton of perks to make it worthwhile, though, I'd say that melee/unarmed is about as overpowered as you can get in the game. No need for cash whatsoever, and the best weapons for their respective slots are available very early. The problem is the incoming damage levels, but as I said, there's perks for that, and if you're not playing a ranged character you never need to bother with a lot of them. (Sniper, gunslinger, commando, etc)
Fallout 3 is exactly what I expected it to be; An incredibly good game that portrays an incredible atmosphere, is very open ended, while trying to be as faithful to fallout as it possibly can without being a black isle game run on the infinity engine with a script written by people who every monty python movie memorized verbatim. It's not fallout, it's not fallout 2, it never could have been either - because, to be honest, most of what we love about fallout is nostalgic and can never be replicated, least of all by a different company. Having said that, though, Bethesda did a great job, and while I don't know if I'd call it Fallout 3, I'd certainly call it Fallout. It would have probably been a better side story than a sequel, and I suspect that would have caused less controversy. It's a good game all the same, and it's everything I was hoping for and more.