Tizen is interesting. A simple and easy to use UI, familiar to Android users, the mobile OS with best performance in low-end hardware. The problem as always are the apps. Tizen supports Android apps through ACL, but until now the only Android app in the Tizen store is WhatsApp. I doubt developers are going to adopt a fourth platform with almost no users, so It seems Android apps is the only way forward. As the adoption increase Samsung would have to pay or develop the apps for the most popular services, because every time the user launches an Android app, the best feature of the OS, performance, suffers.
According to reports, Samsung sold 50.000 Tizen phones in ten days. If that's correct, BlackBerry and WP are in trouble.