I think the main advantage is easy-to-use, decentralized web payments. It's not a browser itself (like Brave) or a browser extension (like metamask) but allows every browser to be a full client of the network without any installation. This reduces the barrier of entry to cryptocurrencies. The team also wants to implement a PayPal like checkout flow for web shops, just fully decentralized.

If you want information on Nimiq, you'd better go to their Discord or Telegram. The BitcoinTalk thread is mostly spammed by ~5 users that write a few posts a day how this project is a scam and everyone saying otherwise is a sockpuppet or team member.