I recall watching this show as a kid & thinking wow. Now as an adult it has lost the wow factor. But keeping in mind when it was made & the fact that they didn't give any thought to a time paradox, I mean sending a soldier back to Roman times with a machine gun & grenades or trying to stop the Titanic from sinking, can you say "lets scew with the future" It's a good show to sit back & watch what they thought sci-fi was about. I like to think off Time Tunnel as a trail blazer for shows like Voyagers, Quantum Leap, Journey man or any other time travelling shows. The 2002 unaired pilot was actually pretty good.
So, taking it for what it was, a '60's take at sci-fi combined with a history class it's not bad...hard to watch by today's standard, butnot bad.