Sometimes you need some testimonials to convince you of a game purchase, and what better way is there to get some insight than from your fellow gamers? As of right now, user reviews aren't a part of the Switch eShop, but some information on Nintendo's website seems to point to that changing soon.
Using the Dragon Quest Builders page on Nintendo.com as an example, at the bottom of the page you can see a "Review this Game" option. Clicking that option checks your account to see if you have the game, and if you've played it for at least two hours. Nintendo also says that "all reviews are from verified players" and "Nintendo does not endorse any reviews on this site."
Certainly seems like reviews are making their way to the Switch eShop. We'll keep an eye out for their implementation, and be sure to share that info with you.