Bushmaster's kit was indeed an ARES kit with the addition of an extra clamp, to prevent the piston housing/chamber from moving/flexing. I still have my ARES plus the clamp (ordered separately from Bushmaster). Can't say much other than it works. Definitely not sexy like LW or other high dollar stuff, but it works every time. No recall I'm aware of of the Bushy kit, but ARES did upgrade their gas cylinder early on due to metal hardness issues with the spigot part of the Gas cylinder. Bushmasters added clamp was a good idea.
Only inferior in that they need access to the piston (take off handguard) to clean. Being able to pull the entire piston op assembly out the front for maintenance is preferable ie. Adams Arms pistons, but since the ARES piston only really needs cleaning @ the 2- 3000 rnd mark (my numbers based on my experience shooting the thing), probably doesn't matter.
If I were to do it again keeping the FSB I'd probably try the OSPREY system, not due to any worries about the ARES with clamp (Bushmaster) but becuse the piston chamber design looks overall closer to the barrel.
For more info on Bushy's kit or if they still have any left, call directly. My guess is the kit just didn't sell so it was discontinued. They may have some left.