By the standards of TNG's key stretch -- seasons 3 through 6 -- this is not an especially remarkable episode. The plot, while good, is not amazing, and the "concept" (in this case, another set of seemingly non-sentient things which turn out to be intelligent) wears a little thin near the end. Nevertheless, the whole thing is executed well enough that it's impossible not to have a good time watching it.
This is, at least to some degree, a Wesley episode, and easily the best one of the show up until this point. Again, the supergenius is gone and instead we have an intelligent teenager who is simply working too hard.
The return of Gates McFadden is very welcome. I'm certainly not a Pulaski-hater, and Diana Muldaur would have improved over time, but from this very episode it's clear that McFadden fit in incredibly well. This is also one of the few episodes to actually look at the Beverly-Wesley relationship, and it does so nicely.
A very promising start!