Not the best. Netflix or Crunchyroll is better.

Its super organized, but it doesnt have popular shows like Neon Genesis Evaligion (sorry, I cant spell very well), Ceres Cestial Legend (Ayashi no Ceres), and not even Sword Art Online. But the breaker for me was that it didnt have K-on. Then I left it. Now of anime, I use Netflix or Crunchyroll, both of them have more shows that are ACTUALLY recognized.

Hullo78 about Viewster, v5.2.4