This would have to be close to my earliest TV cartoon memory, along with maybe 'King Arthur and the Square Knights' and some 60's HB shows. I used to love Q.T. Hush when I was about 5 (mind you this was still 8 or 9 years after it was made). For one thing, the shows went for half an hour, which made them more like mini-movies than the usual HB shorts that filled TV in the late 60's and early 70's.
Judging by the mini-episode available from the link on the profile page, this may have been a case of rose-tinted glasses. In that clip the voice characerisations (especially Shamus) are pretty bad, though I would like to have seen Quincy (the shadow) again.
I'll play it safe and give it 2.0, though as a kid in 1969 I might have given it 4.0!