HaonofRemlu: Not saying anyone will have a spare, but I bought the non-steam version of binding of Issac on accident, and I'm clinically depressed because of my mistake I want the steam version so that I can keep it tracked, but it may just be a dream I will never live to see
Because the game was made with Flash, you're not missing much. The Steam version has many issues regarding the "tracking" of stats you most want. And even if you use a modified unofficial EXE to properly track the achievements (you can find it in the Steam forums), you still will have some issues with the total time played and some achievements not unlocking. I spent over 47 hours playing it, and after a Flash update, I lost my save... and as always, the Steam cloud failed to save my progress and sent me straight to the start of the game with 0% completed.
But if you still want it, the game is always on sale for $1 without the DLC, and less than $2 with it, so you can always sell some trading cards in the meantime until the next sale to get it.