I really like Inkwell in the Tezz build. The 3 reasons that sell it for me are:
1) Shroud
2) Easier to hard cast (recast) that DS
3) Can Pitch to a Force
I know Hurkyl's Recall can bounce him, but he is easier to hard cast (recast) than DS. Not to mention that I run 8 Counter Spells and 4 Duress, most of the time that is sufficient disruption to win. In many cases it's my 12 disruptions cards verses their 1 (Hurkyl's Recall)- If I ran Darksteel it would be my 12 verses up to their 3 (ET, HR, CoV) and that's a best case senario, when you start talking about fish decks with 4 swords and bounce, or decks running 4 Welders.
Just some thoughts.
