They're pricey, which goes with the territory when you pick a Porsche over a Yugo or Kia. I've carried and used British Gimpys, Israeli and Rhodesian MAG58 *MAGgots*, and American M240G and M240E4, worked on the JSSAP Program on what became the M240C coax gun program for Army M60A1 and Abrams tanks, and I've shot the M240L, which I don't care much for.
I've shot both Springfield and Colt Benet-Mercie M1909 machine rifles too, a personal joy since my maternal grandfather was one of the participants at the 1916 raid by Pancho Villa forces at Columbus, New Mexico, while grandda was trying to peddle electrical lighting and generators [*dynamos*] to the railroad there. His diary reflects his dissatisfaction with the double-barrelled shotgun he used that night, and his intention to pick up a pump Burgess or Winchester. He did, and I still have it; grandson'll get it soon.
The 30-round stamped sheet metal feed strip of the Hotchkiss/Benet guns was problematic, but not such a bad deal when you consider the metallurgy of V-fold magazines of the time such as the ten-years-later BAR and Chauchat. American .30-06 ammunition was at least consistent, unlike the French Hotchkiss guns 8mm Lebel ammo, which has also helped ruin the reputation of the CSRG *Chauchat* which I've actually had pretty good luck with, also when fired with decent ammunition.
It'd help if the M240 was about 10 pounds lighter, like the Russian PK/Pecheneg, and fed from both left [Abrams M240C co-ax] or right [Bradley co-ax] side for vehicle guns [not sure about Marine LAVs and Amphib landers] as per the M2 HB with a simple little bolt switch for feeding, or the 1950's-'60s .30 Browning M37 co-ax guns. The recent Navy attempts to turn the M249 SAW into a 7.62 beltfed may be a step in that direction, but notice that the Marines decided that even the M249 was too heavy- with ammo- for the Marine fire team.
We had this conversation about *ideal* GPMGs over at the WeaponsMan blog a month or two black, with good points made by all. Blogkeeper *Hognose* there passed away over the Easter weekend. It was like having a great technical library burn to the ground with all the knowledge within it lost.
My grandfather, mother's dad, served in WWI on the Texas border as a radio intercept tech, catching the German messages to the Mexicans. Later, he was shipped to Murmansk to aid the US contingent against the Reds with his radio intercept expertise.
My experience with the CSRG was when I was helping the new curator of the War Memorial Museum of Virginia accession and clean his massive weapons collection. The had an "American" Chauchat in .30-06 with its straight magazine and it was locked up solid. I carefully built a big spring compressor and eased that little buttstock off and slowly released the spring pressure and figured out how to disassemble the bolt and carrier. I fumbled my way until I realized that the bolt was assembled improperly and I cleaned and oiled everything and reassembled - and then noticed a folded piece of paper inside that tiny buttstock. The note said "My name is Lt. W.D. Wittmer and I carried this gun in France. I assembled it wrong so you'd find this note". Never did find out what happened to W.D. Wittmer but his weapon and note were on display together after that.
Lighter is not necessarily better for machineguns. The mass reduces felt recoil, makes it steadier for better accuracy and control and the heavier barrel makes it a better heat sink so you can shoot it longer before you have to change barrels.
It's better to make my Marines stronger to carry the heavier gun than it is to have a very light gun that fails.