Lost is a particularly good example of a show where the last season is the weakest of all the seasons and not a good representation of why the show is hyped. I also would strongly recommend against using the finale for Battlestar Galactica.
Oh my, I'm still like one of Pavlov's dogs when I hear those magic words "Battlestar Galactica" (as I'm sure you can tell from my avatar). Yes, it would have been a very unfulfilling (and probably confusing) experience to only watch the series finale of that show. But my instincts are about 95% correct when it comes to what TV/movies/books I'll like or won't like, and I made sure that nothing would keep me from watching my BSG week-to-week as it originally aired.
Speaking for myself, there's also a sweet spot that lies squarely between "interest" and "disinterest," and it's satiated by 1 hour rather than satiating my inner couch potato with 40 hours or more. The last thing I really need is another show to be hooked on, and my dog won't tolerate a couch potato. There's a nice trail at the end of my block, and she is quite insistent about using it when the weather is halfway cooperating. Her Pavlovian phrase isn't "Battlestar Galactica," it's "go for a walk."
So while I'm sure the finale-watching approach isn't for everyone, I feel a little better about being informed without being engrossed. But I won't expect to hear a "So say we all!" to that.