The praise he is receiving now is due to political calculations he made in old age. Simon Jenkins in The Guardian observes:

...[Ian Paisley and Gerry Adams] eventually eliminated moderate leaders so they could claim moderation for themselves. They smashed power-sharing so they could share power between themselves. They now pretend that change could not have been faster because the people would not let them. The climate of public opinion in the province was not ready.

That is a lie. These men were the climate, and it was one of systematic bigotry and violence. They chose their methods and terrorised all who opposed them. While religious sectarianism elsewhere in Europe was on the wane, lovers of Northern Ireland had to watch in despair as it drifted to ever greater separatism - territorially, politically and psychologically.

Doubtless, Paisley's retirement will unleash a tidal wave of anecdotes and analysis, and there is no need to rake over everything here; British blogger Oliver Kamm notes one incident which shows us Paisley's true character. Browsing through Martin Dillon's God and the Gun is also instructive, and the book includes a discussion of one interesting association (p.220, date typo fixed):

Paisley...attended the launch of Ulster Resistance, at a secret paramilitary display in November 198[6] after the signing of the Anglo-Irish Agreement. Several days beforehand, Paisley informed me that he could not undertake a broadcast at a scheduled time because he was due to attend a prayer meeting. The 'prayer meeting', in the Ulster Hall in Belfast, was in fact a paramilitary rally to launch Ulster Resistance with Paisley on the platform wearing a red beret. Ulster Resistance was later involved with the UFF/UVF in arms procurement when Paisley was no longer associated with it.

(The later arms procurement involved plotting in South Africa and arrests in Paris.)

It is worth reading this in conjunction with a piece written by Christopher Hitchens a few months ago:

The British laws of libel forbid me to tell what I heard when I was a young reporter in the pubs and back streets of Belfast, but I'll put it like this: Both Paisley and [Gerry] Adams know very well of things that happened that should never have happened. And both of them, in order to arrive at that smug power-sharing press conference, have had to arrange to seem adequately uninformed about such horrid past events. Both have been photographed carrying coffins at political funerals--funerals that were at one time the main cultural activity in each of their "communities." One day, their private role in filling those coffins will be fully exposed. In the meantime, they are the recognized and designated peacemakers.