timppu: The last BoI DLC has one, very negative review, claiming it makes the game too easy and stuff.
So do the DLCs change the base game, or are they all "independent" in that sense?
Meaning, you can safely install all the DLCs and then start playing from the start?
EDIT: I seem to have the original version of Binding of Isaac + Wrath of the Lamb DLC on my Steam account, and possibly the DRM-free version of those in HumbleBundle. So apparently I don't have Rebirth + DLCs on Steam, so buying them from GOG makes sense to me, I guess.
It would have been nice if the original would have been included as an extra with the GOG version, but I guess it doesn't matter much. I have the DRM-free version of those in HumbleBundle then.
I think this post makes some good points on the matter:
Bluddy: I'm going to dispute that review and claim that the last DLC is by far the best one. Here's the story as I see it: the original BOI (Flash version) was a fairly tough rogue-lite with a few exploits. When BOI:Rebirth came out, they made the game a LOT easier in many ways and essentially broke the original design. It became a "getting OP" simulator -- a game about breaking the game and painting the screen with your crazy combos - and it attracted fans who liked that kind of thing. You see, the unique thing about BOI is that it's one of the few games that allows you to pile on endless modifiers. And not minor modifiers either! That kind of thing can easily get out of hand, as you can imagine.
The author of BOI (Edmund) had no idea how to balance Rebirth: it was a gargantuan task. With each DLC he kept adding more insane stuff with serious power creep. There was just no challenge if you knew how the game worked.
The final DLC is the one that restored balance to the force (but not in the Anakin way). It was the first time that other people were authoring the DLC, and they had real solid ideas on how to restore balance to a broken game (I suggested some ideas to them as well). I highly recommend getting the final DLC, as it makes the game one of the best rogue-lites ever. Unfortunately you have to buy all the other DLCs to use the last one.
I wouldn't go so far as to say there was "no challenge" by the end of Afterbirth+, but it definitely pushed the game even more so to the "Getting OP Simulator" part of the equation. I also agree that Repentance does a lot to remedy that. So to address timppu's question more directly, I'd personally recommend starting with no DLC to get a good feel for the game, but if you want to get the DLC from the start, get all three since each requires the previous one to play. It's hard to overstate how much Repentance does for the game.