As far as unlocking websites go, then yes, a VPN can get around country restrictions, although this is legally a grey area. As far as the "improved security", a lot of this is claimed in marketing materials to encourage people to buy the services.
To be clear, a VPN will encrypt the traffic and send it from your PC to the VPN provider where it is decrypted and forwarded on to the internet. The key thing here is that the VPN provider gets the unencrypted version of the traffic so you are putting a lot of trust in them - This is why I would never use a "VPN service" myself (I run my own VPN server on server I control) although others are more than welcome to.
Apart from trying to hide your identity from external websites, the only legitimate use I can think of for such a VPN is if you are browsing on an untrusted public network such as free WiFi available in public places.
At any rate, these services are only designed for short term use such as when on a public WiFi network, they are not designed for or required for use all the time on your home connection. When you are connected to the VPN, all of your traffic is sent to the single VPN server rather than being sent out through several extremely high capacity links from your ISP directly to the destination. As a result, your connection through the VPN will likely be slower and have higher latency than if you are connecting out to the internet directly.
In your situation, all you will get from using a VPN service is a slower connection, less money in your bank account and an illusion of "privacy".
If someone is truly on your network maliciously (which I'm convinced isn't the case) then you have much bigger things to be worrying about than encrypting your outgoing internet traffic.
