Many ISPs apply some sort of traffic shaping to give some types of applications priority over others. For example, some ISPs will heavily throttle P2P and Usenet traffic due to the amount of bandwidth they use.
A VPN is a secure encrypted connection used to connect to a network, typically by employees to connect to the corporate network without risking their data being eavesdropped upon, especially when on public Wi-Fi hotspots, which are generally not secure.
A side-effect with VPN is that an ISP has no way of monitoring what is being sent over the VPN connection, as the data is encrypted. Generally ISPs don't throttle VPN traffic as they risk slowing down legitimate traffic transfers, especially workers who are dialling in from home by VPN. So if you are using an ISP that throttles Usenet traffic, the VPN is a simple way to overcome the restriction, as it will appear just like any other VPN connection to the ISP monitoring equipment.
As Giganwes provides a 14-day trial of the VPN, I would suggest giving it a try and see what the speed is like with and without the VPN. The VPN is a separate connection, so even if you get this package, it is up to you whether you want to connect with the VPN or directly.
Their VPN can also be used as a privacy feature, especially if you use it on a laptop and travel, as it will encrypt your Internet connection once connected to the VPN, which is useful for public Wi-Fi hotspots (including pay-to-use) where it is quite easy to eavesdrop on traffic.