I'm satisfied. True it didn't have the best ending like Soul Eater or even Deathnote, but it wasn't terrible. The main character had a kid and his friend had a kid, thus continuing the cycle.
Let's face it, Aizen did not need a Bankai to be shown. The final stage of that item planted in his chest was powerful enough. Plus the fact that he can't die is also good enough.
As for filling in some of the plot holes, yes I hope (once the anime continues) that the fillers describe why Yhwach was as powerful as he was and why only Ichigo could take him down.