It's not great and it's not terrible either, just inbetween.
I'm a huge DC fan over-all so I'd watch this regardless if it was pretty shit. So far it's been enjoyable, having setting the foundations for how Penguin becomes who he becomes and a glimpse of other characters in their early years (Edward Nigma AKA Riddler). I'm more interested to see if they work on other Batman Adversaries rather than the usual lot that seem to appear everywhere (Killer Croc origins story?).
Pitting this against another DC TV Show Arrow, Arrow definitely wins in terms of entertainment it's running through it's third season and already has shown a number of fan favourite characters (Suicide Squad and Deathstroke with Ra's Al Ghul to appear this season). Not to forget it set-up the introduction for The Flash which is now airing.