Negative effects are limited as only certain powers have been devolved from London to Belfast.NI politicians are an interesting bunch. You also broke our no government record recently (doesn't count though since NI isn't a sovereign state). Any negative effects? Over here it didn't make a difference, plenty of other governments.
Recently a court decided that the Civil Service are unable to make ministerial decisions in the absence of a sitting government and that has immediately impacted a few planned schemes.
At this point in time, there is also very little chance of Sinn Fein going back into government unless the DUP move on issues such as gay marriage, abortion and an Irish Language Act.