Go true to size (ie I am a true size 9.5 so I buy my 577s in a size 9.5)
Comfort Factor Ratings:
Cushioning (Softness): 5/10
Stability (Firmness): 7/10
Cushioning to Stability Ratio: 5:7
Midsole Shape (Foot support): 5/10
The 577 has an ok amount of stability, support, and cushioning. The foam isn't too stiff, but the midsole and outsole are relatively flat.
The 577 utilizes ENCAP.