gistfile1.rb

ruby-1.8.7-p299 > class Vehicle
ruby-1.8.7-p299 ?>  include Mongoid::Document
ruby-1.8.7-p299 ?>  field :horsepower
ruby-1.8.7-p299 ?>  field :top_speed_mph
ruby-1.8.7-p299 ?>  end
 => nil 

ruby-1.8.7-p299 > Vehicle.new(:horsepower => 300, :top_speed_mph => 180).save
 => true 

ruby-1.8.7-p299 > Vehicle.new(:horsepower => 350, :top_speed_mph => 185).save
 => true

ruby-1.8.7-p299 > Vehicle.find(:all).count
 => 2 

ruby-1.8.7-p299 > Vehicle.where(:horsepower.gt => 299, :top_speed_mph.ne => 180)
 => [#<Vehicle _id: 4cd07637aca25f5746000001, top_speed_mph: "180", horsepower: "300">,#<Vehicle _id: 4cd07637aca25f5746000002, top_speed_mph: "185", horsepower: "350">]

# I was not expecting to get back any records with the top_speed_mph of 180
# The first condition always works in another case in which the conditions are reversed