I personally love it. It has my highest KD, and accuracy ratio. I love it's very little recoil and consistent shot placement. Yeah, it usually requires 4 bullets or so. So what? It's a great gun. IMO I don't see what's so good about the swat.
It does between 22 and 33 damage while firing at 720 RPM. The Type 25 also does between 22 and 33 damage, but while firing at 900 RPM. The MTAR fires at 720 RPM, but does between 24 and 40 damage. Just looking at those three assault rifles, the M27 is statistically inferior. The M27 has the slowest TTK in the game.
When you compare the M27 directly to the two other automatic assault rifles, both the SCAR-H and AN-94 do considerably more damage. The SCAR-H fires slower and has considerably more recoil, but can kill in three shots and has considerably more range. The AN-94's first two shots come out at 900 RPM with every following round coming out at 600 RPM. You can burst fire to achieve a higher rate of fire and the recoil is very manageable.
When you compare the M27 to the two semi-automatic assault rifles ... never mind, I won't waste my time.
When you compare the M27 to the two burst assault rifles, it's outclassed by the M8A1 thanks to it's quick bursts and negligible burst delay and by the SWAT-556 thanks to consistent bursts and incredible range.
The M27 isn't useless, just outclassed by every other weapon in the game.
The M27's big flaw isn't necessarily its low time to kill, it's that it has a low time to kill with a low fire rate. Low fire rates can hurt worse than low damage because of accuracy issues; every time you miss a bullet you benefit more from a faster firing gun than slower one, power be damned. It's why the MP7 is better sprayed up close than the MSMC/PDW (even though these two guns have a faster time to kill), and why the M27 is just never going to win a fair fight up close and mid-range.
This is also why the Peacekeeper is so mediocre.
"If I ever kill you, you'll be awake, you'll be facing me, and you'll be armed." - Captain Malcolm Reynolds, Firefly