I found this interesting article in The Blanket by Davy Adams in which he questions whether Sinn Fein are stringing along the DUP and Bertie Ahern for political gain.

Commenting on the DUP,Davy Adams writes that:

"After successfully orchestrating an implosion within the Ulster Unionist Party by continually promising much but delivering little before finally hanging moderate unionists out to dry,one wonders if Sinn Fein might now be trying to employ similar divide-and-conquer tactics in their dealings with the DUP."

Adams goes on to make a comparison between Bertie Ahern and John Hume in relation to the issue of photographs when Ahern appeared to give in to Sinn Fein's demands and he speculates that Sinn Fein may look to do to Fianna Fail what they did to the SDLP.
Adams comments on a point made by Dr.Anthony McIntyre that:

"Sinn Fein is still in a position to trade in the IRA at some later date for electoral gains in the Republic.Might we be witnessing a similar attempt to displace the major party in the Republic?If we are,for more than the obvious reasons I hope it is unsuccessful."

Overall,Davy Adams makes some good points and these issues need to be looked at.
Are Sinn Fein more interested in making life difficult for the other parties rather than accepting their responsibility to the electorate who voted for them?
A good article and worth a read.