Hi,
I've been playing with deckbox for deckbuilding as a replacement for digging out the candidate cards each time, and I think it's very close to being just as (if not more) useful for this. Two suggestions that I feel would improve the deck editor:
1) The default grouping for Enchantment Creatures and Enchantment Artifacts should be Creatures and Artifacts, respectively (it is currently Enchantments). Or at least there should be a feature to toggle this - some people might disagree, but I personally feel it matters more in deckbuilding that these are Creatures/Artifacts than that they are Enchantments. This wasn't really an issue until the Theros block, but now there are quite a few of these cards around.
2) Allow checking off multiple cards and moving them all to the sideboard (or back to the main deck) as a Card Action via the button at the top, instead of having to click the little red arrow next to each card individually (which actually clears all your checkmarks!).
Thanks for your consideration