It's not the best episode, but it's certainly not the worst (Where in the world is Spock's brain?!!) Corbett seemed lost in character. I usually like him, but not his finest acting moment here.
At their best, those two shows were great. At their worst, however (the last season of TOS was hit and miss while the first season of TNG was really bad and the second season was a mixed bag), they stunk up the joint. While maybe not with the same highs, Deep Space Nine was consistently good from beginning to end, IMO.I give TNG a lot of grief and still prefer TOS, but man TOS has some real clinkers.