I really enjoyed HTTM, it was brill, just totally stupid. No pretending it was possible or explainable, just; "oh right, the hot tub must have sent us back in time," and if you're willing to accept that why not accept the whole film as being jolly good fun? The first joke seemed gross and out of place though, dog-crap jokes? Puh-leaze!*
The only other niggle I had was that the girls they got off with twenty years ago were still the same age when they got back to the future.
That reminds me, Crispin Glover is still ace.
*The conclusion of episode two of HR was brought about by Peter and Sam engaging in a dog shit battle with an enemy.