I loved this show, so okay - its got more time-travel holes than say the Terminator or Star Trek series, and it doesn't concetrate on the physics, science and stuff as it should do - and yes, perhaps at the end it became a religious thing turning to god, etc...
You can say all that, but I still loved this show, it was great viewing, most of the early episodes were really inspiring, intresting, even some could argue intelletucal - but the shows became too formalic, too much the same. The writers injected more ideas with the introduction of an evil leaper (possibly from the future, or from a foreign power - we never get to find out), and the interesting social commentary it sutley presents.
Its more family viewing than say the slam bang action, over the top sci-fi special effects laden technobabble that you get say from Star Trek or from other shows, but it has heart, it has enjoyment.
I've started to notice that a lot of shows copy the idea of leaping around - StarGate SG1, Sliders, and so much more...they more or less sound like the same thing, but they lack the heart and social commentary that this series had.
The last series (or last but one) reintroduced the character of Dr.Sam Beckett - we get to see him leap into Lee Harvey Oswald (who we see as an unstable character - Beckett struggling to leap out of his body before Oswald/Beckett shoots JFK), then in the last episode he leaps into himself - and decides to devot his life to fixing the past - as god's worker.
Although it was a pretty touching end, and we got hints of a TV/movie sequel (his daughter was working on the Quantum Leap project, etc - this could have meant his daughter trying to look for him), it never materialised - which is a real shame, most of the fans were upset that Beckett never returns home - they wouldn't accept it...I certainly didn't - I kept thinking there was a twist in the end titles were it said: "Dr.Sam Beckett never returned home" or similar...I always thought - well that could mean "because he never left home" or something.
Anyway, this is a great TV show, and as more and more producers try and fail to copy this show - we, as fans, can only hope a one off feature film or similar. They owe us that at least.