I saw the new 576xp at the dealer the other day. I was there to pick up a sprocket but my CAD started to kick in. Same silver side cover as the 346xp. Felt good in the hands. The USA sight doesn't even list the saw. 
Hopefully someone on AS will get one in the near future and give us a report. Here is some info off a U.K. site.
HUSQVARNA 576XP
Our most advanced saw for professional users who require peak performance. Larger displacement, higher peak power and torque and even better ergonomics combine to ensure maximum productivity.
X-TORQ
The X-TORQ engine design increases torque over a wider rpm range, providing maximum cutting power.
Improved handle design
The rear handle is asymmetrically designed with comfort inserts for a more stable and less tiring grip.
Optimized saw body
No protruding parts, a smooth underside, rounded starter cover and well-protected controls all make the saw easy to handle.
Durability
Available with heavy-duty air filter.
Air Injection
Centrifugal air cleaning system for reduced wear and longer operating time between filter cleanings.
Smart Start
The engine and starter have been designed so the machine starts quickly with minimum effort. Resistance in the starter cord is reduced by up to 40%.
Engine
Cylinder displacement 4.48 cu.inch / 73.5 cm³
Maximum recommended engine speed 13 600 rpm
Fuel tank volume 1.48 US pint / 0.7l
Oil tank volume 0.78 US pint / 0.37l
Oil pump type Adjustable flow
Cutting equipment
Chain pitch 3/8"
Recommended bar length 16-32" / 40-80 cm
Ergonomics
Sound level 107 dB(A)
Noise emissions, LWA 115 dB(A)
Vibrations, front/rear handle 3.2 m/s² / 3.4 m/s²
Overall dimensions
Weight without cutting equipment 14.9 lbs / 6.8 kg
Hopefully someone on AS will get one in the near future and give us a report. Here is some info off a U.K. site.HUSQVARNA 576XP
Our most advanced saw for professional users who require peak performance. Larger displacement, higher peak power and torque and even better ergonomics combine to ensure maximum productivity.
X-TORQ
The X-TORQ engine design increases torque over a wider rpm range, providing maximum cutting power.
Improved handle design
The rear handle is asymmetrically designed with comfort inserts for a more stable and less tiring grip.
Optimized saw body
No protruding parts, a smooth underside, rounded starter cover and well-protected controls all make the saw easy to handle.
Durability
Available with heavy-duty air filter.
Air Injection
Centrifugal air cleaning system for reduced wear and longer operating time between filter cleanings.
Smart Start
The engine and starter have been designed so the machine starts quickly with minimum effort. Resistance in the starter cord is reduced by up to 40%.
Engine
Cylinder displacement 4.48 cu.inch / 73.5 cm³
Maximum recommended engine speed 13 600 rpm
Fuel tank volume 1.48 US pint / 0.7l
Oil tank volume 0.78 US pint / 0.37l
Oil pump type Adjustable flow
Cutting equipment
Chain pitch 3/8"
Recommended bar length 16-32" / 40-80 cm
Ergonomics
Sound level 107 dB(A)
Noise emissions, LWA 115 dB(A)
Vibrations, front/rear handle 3.2 m/s² / 3.4 m/s²
Overall dimensions
Weight without cutting equipment 14.9 lbs / 6.8 kg
