I saw a video by kingscrusher in which he recommended this opening, and I've started to play around with it and have had some positive results.

One main continuation that I have been encountering is:

2. c4 e5
3. dxe5 dxe5
4. Qxd8+ Kxd8

which looks very tempting to lower rated players who are playing white because it breaks black's castling. However, I believe that black has an advantage here, and according to the 365chess.com database, black wins about 51% to white's 13% in a sample of over 800 games (for whatever that is worth). Also, even if black does not have an advantage in the optimal play sense, black will have much more familiarity with the position than the typical Queen's gambit player who sees 1. ...d5 all day.

My plan for black in this position to play c6, a5, Na6, Nc5, Kc7 as appropriate, and it seems to result in a good position.

I realize that this line will often transpose into other openings if white plays something other than 2. c4, but I think that comes up enough for this to be a decent surprise weapon.

Thoughts?

Roman's Lab recommended this line for absolute beginners. You won't get any advantage- in fact often you'll get an inferior game- but you'll usually reach a playable position.

The stats that show a big winning percentage for Black look pretty suspect. In reality the trade of queens is very drawish.

I was suspicious of such a high winning % too, but Megabase 2009 shows similar numbers after the trade of queens (14% W win, 35% draw, 51% B win). It turns out that the stats are really just a reflection of the weakness of the white players who enter this line in OTB play, rather than any objective value of the opening. In spite of such a huge score, black is only performing at his rating level vs the 2 most common 5th moves (Nc3 and Nf3).

That said, there's almost certainly nothing wrong with 1...d6 as long as you're willing to play a KID/Old Indian/Pirc.

Nunn's Chess Openings lists 1. d4 d6 2. c4 e5 3. dxe5 dxe5 4. QxQ KxQ 5. Nf3 f6 6. Nc3 Be6 7. b3 c6 as being an equal position and the main line for this variation.

I probably wouldn't recommend spending much time learning such an obscure line. You're really dependent on white playing both 2. c4 and 3. dxe5, and even so, you're getting at best an equal position. Nf3 for white, played both on the second move and third move (after d6 or after e5) looks suitable.

Also, if I were faced with 1. d4 d6, I would strongly consider this an invitation to play against the Pirc (1. e4 d6 2. d4) and I could transpose quite easily with 2. e4. You'd have to be comfortable playing that opening too, and I imagine you'd be faced with (1. d4 d6 2. e4) about 5 or 6 times as often as you would against (1. d4 d6 2. c4 e5 3. dxe5) in tournament play.

3.dxe5 is a pretty lame line with no chance of getting an advantage.
3.Nf3 e4 4.Ng5 etc is a better line

or 2.Nf3 Bg4, 2.e4 etc

Like has been said, black's good results in the queen exchange line are going to be a result of weak white players, or players looking for nothing more than a draw (which is a great way to get a loss), choosing that line rather than any merit of the opening itself. I really couldn't recommend this opening. The positions especially after 1. d4 d6 2. Nf3 are very difficult for black unless you just transpose to pirc/KID in which case there's little point in playing 1. .. d6 in the first place.

well after 1. d4 d6 2. c4 e5 3.dxe5 Black may actually already be a tiny bit better because of the "better" pawn move (e5 compared to c4). As white is in no position to exploit the black Kd8.

Compare Anderssons line 1. c4 c5 2. Nf3 Nf6 3. Nc3 d5 4. cxd5 Nxd5 5. e4 Nxc3 6. dxc3 Qxd1+ 7. Kxd1.
Of course most of his success came from being better at endings than his opponents but he probably did argue that black's c5 can now be shown as weakening.

You can avoid the Sämisch, 4 pawns and some other systems without Nf3.

edit: the comment with the better pawn move of course only applies when the d-pawns and the Qs are exchanged. Otherwise i take the c-pawn move over the e-pawn all day long

Right, it can provide some useful move order things in the pirc/KID but you're still playing the pirc/KID at the end of the day. Also, who would want to avoid the samisch or 4 pawns!

Nigel Davies has a DVD on 1. d6 universal I bought because of my regular usage of the Pirc -

He points out that this exchange variation leaves black with a better grip on the center and a chance to weaken the queenside after b3 with a5-a4 -

but yah, for white to trade off his opening advantage so quickly suggests he's not the sharpest tack in the shed neither