The app "Letters|友人・知人への紹介&口コミを広げて売上アップ" is generally well-received by merchants. They appreciate its simplicity and effectiveness in facilitating customer referrals, which is seen as a promising way to increase customer acquisition. Merchants find the app easy to use and suitable for expanding their customer base through word-of-mouth marketing.
Overall, "Letters|友人・知人への紹介&口コミを広げて売上アップ" is praised for its ease of use and the ability to effectively drive new customer acquisition through referrals. While there are some areas for improvement, particularly around customer registration processes and initial user learning curves, the app delivers significant value in expanding market reach and increasing sales through enhanced word-of-mouth promotions.