I have mixed feelings on this.
Firstly, I certainly don't believe that Iran will commit a terrorist attack on the West.
Given that Iran has backed a regime in Syria which terrorises its own civilians with barrel bombs, even if Assad won't send suicide bombers to kill our citizens like ISIS or Al-Qaeda, it's not exactly a time to call the IRI 'good'. I appreciate that Qassem Soleimani and his Quds Force has been vital in pushing back ISIS, I really hope they won't commit any more crimes against Sunni civilians in Iraq, as that discriminatory attitude was what led many Sunnis to support, or at least tolerate or not resist, ISIS. If Iran manages to discipline Shia militias to treat all Sunni civilians with respect, then Iran's help is constructive. If not, it'll only lay the seeds for another war in Iraq.
There is no perfect player in the complex wars in Iraq and Syria. Even the Iraqi Kurds haven't been as unified in the past as we thought (-->KDP-PUK war of 1994-1997).
I am an objective observer who attempts to offer a fair opinions on all parties in a conflict. I do not support Israel either, its long list of crimes against Palestinian civilians should have been condemned long ago...