I wrote a long review on Steam, comparing this game to World of Warcraft. Unfortunately, there's a limit of characters here, so I couldn't paste it. Nevertheless, here's an overview of the positives and negatives of Elder Scrolls Online (ESO):
Positives
+Stunning graphics
+Utterly superior storylines to WoW
+Character attire and skin customization
+Exploration/Traveling in the world is enjoyable
+At it's normal price of $20 (Steam) it's nearly robbery
+Very strong replayability
+So-Much-Content (High hundreds of hours!)
++No monthly subscription needed (unlike other MMORPGs-like WoW)
Negatives
-A sizeable good number of skills for Templar (the class I play) could be better/improved
-Fighting is not as sophisticated nor as fulfilling as it is in some of the other MMORPGs or RPGs
-Like its competition (including WoW), ESO's store is too costly
-Off-putting starting point (You'll have to play beyond the starting point/area to experience and feel how great the world and game really is, but the starting point/area, almost neuters that until you get to Vvardenfell)