I'm not suggesting that people looking for feedback should buy the product first. I'm suggesting that the people giving the feedback should have experience with the product in question. The feedback from someone who hasn't bought the product or operated the product has very little credibility or substance.
If they're saying the game is trash, maybe that's true, but I think people can still give valid opinions about whether they think the DLC is worth 20 dollars without having played it.
Spoiler I have not played the DLC, but from what I've heard it sounds that it doesn't have enough to entice me at that high of a price. I don't like what they did to the look of the vampires, I don't like the the confusing as all get-out situation we have now with vampires as to what clans they belong to, I hate the "overhaul" they made to vanilla vampires, I think that two of the things they've been publicizing (Fletching and Dragonbone weapons) should have been included in the vanilla game, I'm bothered by the fact that the dragon diving through ice in the trailer is a specific one time event, rather than a new behavior script that any dragon can make use of, and there's some other serious issues I have with the design choices of this game, but I won't because I don't want to ramble too much.
The point is, even without playing it, hearing about a lot of these things have notified me that I'm better off not getting the DLC for now (which is all well and good, because Bethesda shows no signs of releasing it on PS3 anytime soon). Even if it was released this Tuesday, I wouldn't get it because there's enough stuff I know I wouldn't like to make me feel that that 20 dollars would be better spent getting something else, like Deus Ex: Human Revolution. I'd also rather wait to get the DLC until I have a PC that could competently run Skyrim, and wait until someone mods a Vampire Overhaul that irons out some of the major design flaws that I feel Dawnguard has (especially those considering the vampires).
Not looking at the story aspects, but just looking at some of the additions and alterations, there's a lot of stuff I like about Dawnguard, but there's also a lot I don't like. Right now it seems to be split 50-50, and for me personally, 20 dollars is too high a price to fork over for DLC that I feel I'll hate half the content of. So for me, it isn't worth it.