As far as used spotting scopes go the old Bushnells, Baush & Lomb and the Redfield are good scopes. But they are almost impossible to find.
I too had a Simmons and had the same experience you did. They are OK for a Bullseye pistol shooter, but not for rifle shooting or hunting.
The best scope is the Leupold, Gold Ring. They work well in low light, Lifetime warranty on the scope, regardless of who purchased it, compact and easy to carry for hunting. They hold their value, and are generally passed down as a legacy to heirs.
They are expensive, but because of their quality once you own one its easy to justify having spent the money. I own one so I know its true.
I have no experience with Nikon, but I have heard and have reason to believe that they are a good quality glass also. I don't know about their warranty, but I have seen them offered on E-Bay.