It is one of the few weapons you have to level to get.
Eitherway, it is far from good, so why bother?
I agree, that the AMR is not that great compared with other sniping tools. I personally would like to suggest the Sniper Rifle instead, and I would like to provide a quick recap for yall on where to find one laying around for free at early levels (at the end of my rant).
There are hypes on the internet for this weapon (the AMR), You Tube, character building guides based on the weapon, even in the game some NPCs would comment on how the ARM is great against Deathclaws. Look at this video making the AMR looks lovely: http://www.youtube.com/watch?v=9J5CM-mbLNE
But when I eventually got it in my mid twenty for my Very Hard and hardcoe game to hut Dethclaws, I was dis-pointed because of the following reasons:
1) Slow reload time and firing rate.
Even though I believe the AMR is more powerful in single shots than some other sniping tools in the game, this effects DPS. Though I understand, for any other better skilled gamers, you are meant to snipe with sneak and complete your kill in one shot, but in reality, I am just not that great of an aim.
2) 20 pound worth of weight.
A bit heavy for my personal liking even I have Strong Back, Pack Rat and can carry a total of 260 pound, 20 pound would have provided me the space for a mooded Sniper Rifle at 5 pound in weight instead of 8 and one or two weapons for repair during travel.
Instead, due the the higher firing rate of the Sniper rifle, you can be comfortable with more different combat situations, with optional silencer. You can see the combat effectiveness quite immediately if you experiment the two weapons on Boone the companion (Edit: by giveing him the weapons to use, not killing him).
You can get a free Sniper rifle quite conveniently in Camp Mcarren, there is one laying on top of a bunk bed; in a tent that is directly facing the main building doors that are closest to you when you first enter the Camp.
Good luck!