I think it all depends on the OP's feelings towards TOS. If the OP finishes TOS and is thirsty for more then I'd say TAS is a must-see.
Personally, I adore it. M'Ress is one of my favourite Star Trek characters ever because I'm an elitist cunt. The writing quality is generally very good and makes up for the subpar animation, and it's a thrill to hear the cast back.