Lately, I've been marathoning various series - as you surely know ;) - and I realized one thing: I prefer watching series that already ended or early seasons of shows currently on air to watching series "live", together with the rest of the fandom. Why? That way, I can avoid pissy, whining fans.
Example: I watched due South for the first time a long time after it actually ended. I missed the whole RayV vs. RayK war and I'm so glad! I enjoyed the show much more that way, let me tell you.
These days, where ever you go, people whine about SPN and its lack of over-reaching Dean!plots, about WhiCo and its plot holes, about NCIS and Ziva... And I'm getting fed up fast. I'm not saying these shows are perfect, far from it actually. I'm not saying that people shouldn't point out what they don't like. I would prefer a more cohesive storyline focusing on Dean, I would like the WhiCo writers to focus more on Peter&Neal again and less on the team, I would like to see DiNozzo as something more than a class clown - but overall, these shows are extremely enjoyable and I just don't get why people who call themselves fans of the shows need to nitpick everything.
If the show bothers you so much, then don't watch it! To watch something only to tear it apart and mock it, sometimes even before the episode airs, saying things like "Let's watch this train-wreck" etc. is extremely annoying.
I dropped many shows I didn't like - lately it was Bones, for example - and from time to time, I go back to check them out, to see if they got any better, worth watching again, or not. But I don't haunt every article related to shows I don't like with derisive comments.
So, I prefer watching shows on DVD, knowing that only their fans will be dropping comments on my entries to fangirl together with me. That's what I love so much, like when I was watching ST:TOS S1 and I could squee and bounce together with peeps who don't follow any of my current shows.
More power to DVD marathons!