I have been doing varmint control with airguns for long time now. They are cheap and effective enough. Although the Gamo is .177 , so it is not the .22 like some more expensive airguns are, added velocity makes up for it and is enough for kill, with almost any pellet.
That Gamo I would consider to be actually one of the, if not the, best airgun for the money. Especially considering the fact that you get full package, scope and scope mount included.