I have Nikon's on all my guns and have been very pleased. There optic quality is excellent, and the scopes are rugged. I wouldn't get anything that wasn't in the Monarch, Monarch Gold or Tactical series though. Buckmasters aren't quite as good topically.
Monarch 6.5-20X44 is the way to go.
My 2 cents.
I would disagree with Cobber slightly. The new Nikon Buckmaster 6-18x40 is a great scope. It offers an upgrade to the lower powered Buckmaster with improved lens coatings. The 6-18x40 offers 92% light transmission, compared to the 95% on the Monarch and 88% for the lower powered Buckmaster. If you are looking for a high powered scope at a very reasonable price with very good quality, it is hard to beat this scope and I would highly recommend the new Buckmaster 6-18x40 or the 4-12x50.