I've bought 4 rifles from there so far and have not had a problem with the sight or vendors.
My last purchase included a scope which the vendor stuck on to a track attention to the sale and it was broke but after a phone call and short discussion the vendor discounted the value of the scope from the sale price which made me happy since I didn't want the scope to begin with.
The vendors don't like to get bad sale ratings so they will try with in reason to make things right should there be a problem