The Dwan Edwards signing was an excellent one. He is the quintessential 3-4 DE gap-filler. I couldn't care less about failed physicals with other teams. If there is one person all Bills fans should trust in this organization, it's Dr. Andrew Cappuccino (remember Kevin Everett?), who gave Edwards a clean bill of health.
To answer your question, I think Buddy Nix is an incredibly intelligent football mind and has shown time and again an ability to spot the right players. I've been down on the Bills the past 10 years, but Nix has brought a ray of hope with his no-nonsense approach and knowledge of what it takes to succeed.