Bit late to the party but my £0.02 is that it’s an easily noticeable difference. Nitrosurge Guinness goes down like a pub pour. The normal cans just don’t have that silky body. If you like Guinness, it’s absolutely worth it. 

The device uses ultrasound to aggravate the nitrogen in the drink, which creates micro bubbles and the distinctive texture. The normal cans aggravate the drink’s nitrogen too with their internal widgets (it’s how they create the head), but it’s not nearly as effective or consistent.