MTG Salvation

Here's the situation. I see at least 3 competitive deck types revolving around artifacts as AEther Revolt is going to be released. I am guessing that number might even grow before the month is over. I'm considering running either R/U or R/B and possibly U/B. So keep in mind that cards like Fragmentize and Natural State will not be available to me. My question is, how good of a sideboard card do you consider Release the Gremlins turning out to be? Also, if you can think of another answer to artifacts within the Grixis color scheme, it's much appreciated. Obviously this is all speculation, but it might help me work out a deck for this month. All constructive input is appreciated, thanks.