From my understanding, Jason is about the only one here who watches/watched the show, so he might like my first impressions on a show I know next to nothing about. Otherwise, as long as I watch the show, this'll probably just be a thread of me ranting alone, which I'm cool with.
There will be spoilers as I discuss each episode, I'd suspect, but given that I literally don't know anything about the show (I cannot stress this), please do not spoil anything that happens in later episodes/seasons.
So, onto Season 1, Episode 1, "Pilot"
The gist I'm getting is that this show is a series-length version of Frailty (2001). How they hope to keep it interesting, I have no idea. There's no way they can keep up the "Let's go on a road-trip and look for dad" plot for even a season without getting repetitive. The prologue was decently creepy (until the hideous special effects during the mother's death), so that's a plus.
I only have a few words about Sam's girl Jess:

She was smoking (get it? she died by fire at the end), and it's a shame that she left the series so soon. That said, she has no place in a road-trip between brothers, so good riddance. Still, she was #smexy.

Both Sam and Dean seems likable. Sam admittedly loses points for dissing Black Sabbath and Metallica (Motörhead I could take or leave), and I have a feeling he'll just be moping and super-pissed these next few episodes, but I suppose that's understandable. Better to hunt demons than go to law school, though - that's what my grandfather always said.
Dean's pretty cool. Fake credit cards, fake identities for various law agencies, solid guy all around. That "squeal like a pig kind of trouble" line was amusing. And he works decently well with Sam, so that's looking good.
I'm taking note of what Sam said, from this quote: "You remember the poltergeist in Amherst? Or the Devil's Gates in Clifton?" - no idea if these are just throwaway lines, or if they have any relevance, but it's good to jot down.
The weeping woman, or woman in white, wasn't the most amazing ghost/monster/supernatural thingy to open the series with, but she was done well. I don't think she should be able to force herself onto a man and call that being unfaithful, though - strikes me as cheating. As Dean said, she was a bitch. At least she's at peace (INB4shecomesbackattheendoftheseasonasasurprisevillainwhokidnappedtheirfatherforsomereason).

All-in-all, a solid episode. I like how it looks to lead into the next on, taking place in Colorado. I sort of wonder if the police are going to be looking for them, as another subplot.
More importantly, I sort of wonder what happens when they find their father, and how they've managed to prolong this series into 15 seasons.
That's it for now, folks.