FAL is my staple gun. I only have one kit without it - that kit being my Holo M16 w Stopping Power, which is my only Stopping Power Kit. To give context too, I pretty much play only TDM.
One thing I have observed (and given light of the new video showcasing the Holo M16 is more accurate than the RDS M16) for some reason, I've always felt that the FAL was easier to use with a Holo than an RDS. I'm not sure if it's just in my head, but if you're struggling with the FAL, trying using Holo instead of RDS assuming you don't prefer Iron Sights.
Reason why I like the FAL so much is that it opens the door for using other Tier 2 Perks like Hardline, Cold Blooded and Danger Close. One thing to note is that it does have some recoil, so you have to adjust to that. The further away you are from the target, the more you'll have to fire off in short gaps. For instance, if you're trying to pick off a sniper off in the long, long distance - you'll have to spread your shots out unless you get a headshot in. If you fire in quick successions the recoil will make you miss badly. In such cases, don't be surprised if your target simply moves away.
Also, just remember that in most short to mid-range cases, you're only going to need two shots to take them down. Just to give a bit of the background, the base damage for the FAL is 50 damage points per round. The M16 with Stopping Power is 56 damage points per round. Thus the FAL's actually quite effective, if you can adjust to the recoil and get over the single shot fire. But it all really depends on your playstyle too - if you're more of the rushing type, a fully automatic gun like the Scar is probably the way to go.