The big problems with Meltdown are...
1. You can't turn it off.
2. If your only source of damamge is energy (which mine was) you are screwed if a lot of things charge you.
3. If your follower is melee (which mine was) they will rush right into the thick of things...
4. if you kill one target it splashes... if target two dies from the splash he blows up... if target three dies from the combined one, and two targets then he blows up... leaveing you dead as a door nail.
As a side note I had a huge problem with this taking out Ceasar. First I blew up Veronica into little bits when everyone exploded. Then I left her outside and went in alone... all that did was cause me to blow up also. I had to leave C4 outside of his tent as a trap, and have him chase me out side... I never could find his corpse not sure it ever came back down I may have used to much C4 >.> lol.
Meltdown is kinda fun. You can work around it if you are willing to, but have back up weapons that are not energy for low HP things that chareg at you. I died to a pack of Gecko's near Goodspring of all places due to a misplaced Meltdown...
Spoiler
Also if you are doing hardcoe (which I was -_-) trust me Meltdown is not worth it... It almost always leads to a broken limb. I went Yes Man, and at the start of the Hoover Dam fight I was fighting Rangers when the Great Khan just poped out next to me. So I swung on them, and one shooted one of them next to me. The whole end battle I had fight with a broken Head, Chest, and Left Foot... Fun times.
***EDIT***
As the guy ahead of me said the RCW is about the only laser weapon that is VAT'able. However Laser rifle + scope, or the YSwhatever more then make up for the lack of VAT's.